[android] enable image shared element transition for API 21+22

There's an Android framework bug (#224270) on these APIs that causes a NPE
when the shared element is not visible anymore when returning.
Since we know restore the list position, the shared element should be
visible and thus not produce NPEs anymore.

bramble-android/src/main/java/org/briarproject/bramble/account/AndroidAccountManager.java

@@ -9,22 +9,19 @@ import org.briarproject.bramble.api.account.AccountManager;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.util.IoUtils;
 
 import java.io.File;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
 import javax.inject.Inject;
 
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.IoUtils.deleteFileOrDir;
-
 class AndroidAccountManager extends AccountManagerImpl
 		implements AccountManager {
 
 	private static final Logger LOG =
-			getLogger(AndroidAccountManager.class.getName());
+			Logger.getLogger(AndroidAccountManager.class.getName());
 
 	private static final String PREF_DB_KEY = "key";
 
@@ -40,7 +37,7 @@ class AndroidAccountManager extends AccountManagerImpl
 		appContext = app.getApplicationContext();
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	@Override
 	@Nullable
 	protected String loadEncryptedDatabaseKey() {
@@ -50,7 +47,7 @@ class AndroidAccountManager extends AccountManagerImpl
 		return key;
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	@Nullable
 	private String getDatabaseKeyFromPreferences() {
 		String key = prefs.getString(PREF_DB_KEY, null);
@@ -59,7 +56,7 @@ class AndroidAccountManager extends AccountManagerImpl
 		return key;
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	private void migrateDatabaseKeyToFile(String key) {
 		if (storeEncryptedDatabaseKey(key)) {
 			if (prefs.edit().remove(PREF_DB_KEY).commit())
@@ -84,7 +81,7 @@ class AndroidAccountManager extends AccountManagerImpl
 		return PreferenceManager.getDefaultSharedPreferences(appContext);
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	private void deleteAppData(SharedPreferences... clear) {
 		// Clear and commit shared preferences
 		for (SharedPreferences prefs : clear) {
@@ -100,7 +97,7 @@ class AndroidAccountManager extends AccountManagerImpl
 			for (File child : children) {
 				String name = child.getName();
 				if (!name.equals("lib") && !name.equals("shared_prefs")) {
-					deleteFileOrDir(child);
+					IoUtils.deleteFileOrDir(child);
 				}
 			}
 		}

bramble-android/src/main/java/org/briarproject/bramble/battery/AndroidBatteryManager.java

@@ -19,7 +19,9 @@ import javax.inject.Inject;
 import static android.content.Intent.ACTION_BATTERY_CHANGED;
 import static android.content.Intent.ACTION_POWER_CONNECTED;
 import static android.content.Intent.ACTION_POWER_DISCONNECTED;
-import static android.os.BatteryManager.EXTRA_PLUGGED;
+import static android.os.BatteryManager.BATTERY_STATUS_CHARGING;
+import static android.os.BatteryManager.BATTERY_STATUS_FULL;
+import static android.os.BatteryManager.EXTRA_STATUS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
 
@@ -46,8 +48,9 @@ class AndroidBatteryManager implements BatteryManager, Service {
 		IntentFilter filter = new IntentFilter(ACTION_BATTERY_CHANGED);
 		Intent i = appContext.registerReceiver(null, filter);
 		if (i == null) return false;
-		int status = i.getIntExtra(EXTRA_PLUGGED, 0);
-		return status != 0;
+		int status = i.getIntExtra(EXTRA_STATUS, -1);
+		return status == BATTERY_STATUS_CHARGING ||
+				status == BATTERY_STATUS_FULL;
 	}
 
 	@Override

bramble-android/src/main/java/org/briarproject/bramble/network/AndroidNetworkManager.java

@@ -13,7 +13,8 @@ import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.network.NetworkStatus;
 import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.system.Scheduler;
 
 import java.util.concurrent.Future;
@@ -33,17 +34,16 @@ import static android.net.ConnectivityManager.CONNECTIVITY_ACTION;
 import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.os.PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED;
-import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
 
-@NotNullByDefault
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 class AndroidNetworkManager implements NetworkManager, Service {
 
 	private static final Logger LOG =
-			getLogger(AndroidNetworkManager.class.getName());
+			Logger.getLogger(AndroidNetworkManager.class.getName());
 
 	// See android.net.wifi.WifiManager
 	private static final String WIFI_AP_STATE_CHANGED_ACTION =
@@ -56,7 +56,6 @@ class AndroidNetworkManager implements NetworkManager, Service {
 			new AtomicReference<>();
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
-	@Nullable
 	private volatile BroadcastReceiver networkStateReceiver = null;
 
 	@Inject
@@ -90,8 +89,9 @@ class AndroidNetworkManager implements NetworkManager, Service {
 
 	@Override
 	public NetworkStatus getNetworkStatus() {
-		ConnectivityManager cm = (ConnectivityManager) requireNonNull(
-				appContext.getSystemService(CONNECTIVITY_SERVICE));
+		ConnectivityManager cm = (ConnectivityManager)
+				appContext.getSystemService(CONNECTIVITY_SERVICE);
+		if (cm == null) throw new AssertionError();
 		NetworkInfo net = cm.getActiveNetworkInfo();
 		boolean connected = net != null && net.isConnected();
 		boolean wifi = connected && net.getType() == TYPE_WIFI;

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPlugin.java

@@ -24,6 +24,7 @@ import java.io.IOException;
 import java.security.SecureRandom;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.BlockingQueue;
@@ -47,11 +48,9 @@ import static android.bluetooth.BluetoothAdapter.STATE_OFF;
 import static android.bluetooth.BluetoothAdapter.STATE_ON;
 import static android.bluetooth.BluetoothDevice.ACTION_FOUND;
 import static android.bluetooth.BluetoothDevice.EXTRA_DEVICE;
-import static java.util.Collections.shuffle;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 
 @MethodsNotNullByDefault
@@ -59,7 +58,7 @@ import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 
 	private static final Logger LOG =
-			getLogger(AndroidBluetoothPlugin.class.getName());
+			Logger.getLogger(AndroidBluetoothPlugin.class.getName());
 
 	private static final int MAX_DISCOVERY_MS = 10_000;
 
@@ -260,7 +259,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 			appContext.unregisterReceiver(receiver);
 		}
 		// Shuffle the addresses so we don't always try the same one first
-		shuffle(addresses);
+		Collections.shuffle(addresses);
 		return addresses;
 	}
 

bramble-android/src/main/java/org/briarproject/bramble/plugin/tcp/AndroidLanTcpPlugin.java

@@ -32,19 +32,17 @@ import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
-import static java.util.Objects.requireNonNull;
-import static java.util.logging.Logger.getLogger;
 
 @NotNullByDefault
 class AndroidLanTcpPlugin extends LanTcpPlugin implements EventListener {
 
-	private static final Logger LOG =
-			getLogger(AndroidLanTcpPlugin.class.getName());
-
 	private static final byte[] WIFI_AP_ADDRESS_BYTES =
 			{(byte) 192, (byte) 168, 43, 1};
 	private static final InetAddress WIFI_AP_ADDRESS;
 
+	private static final Logger LOG =
+			Logger.getLogger(AndroidLanTcpPlugin.class.getName());
+
 	static {
 		try {
 			WIFI_AP_ADDRESS = InetAddress.getByAddress(WIFI_AP_ADDRESS_BYTES);
@@ -68,8 +66,10 @@ class AndroidLanTcpPlugin extends LanTcpPlugin implements EventListener {
 		// Don't execute more than one connection status check at a time
 		connectionStatusExecutor =
 				new PoliteExecutor("AndroidLanTcpPlugin", ioExecutor, 1);
-		connectivityManager = (ConnectivityManager) requireNonNull(
-				appContext.getSystemService(CONNECTIVITY_SERVICE));
+		ConnectivityManager connectivityManager = (ConnectivityManager)
+				appContext.getSystemService(CONNECTIVITY_SERVICE);
+		if (connectivityManager == null) throw new AssertionError();
+		this.connectivityManager = connectivityManager;
 		wifiManager = (WifiManager) appContext.getApplicationContext()
 				.getSystemService(WIFI_SERVICE);
 		socketFactory = SocketFactory.getDefault();

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPlugin.java

@@ -8,7 +8,8 @@ import android.os.PowerManager;
 
 import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.network.NetworkManager;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.system.Clock;
@@ -25,10 +26,10 @@ import javax.net.SocketFactory;
 import static android.content.Context.MODE_PRIVATE;
 import static android.content.Context.POWER_SERVICE;
 import static android.os.PowerManager.PARTIAL_WAKE_LOCK;
-import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.TimeUnit.MINUTES;
 
-@NotNullByDefault
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 class AndroidTorPlugin extends TorPlugin {
 
 	// This tag may prevent Huawei's power manager from killing us
@@ -51,7 +52,8 @@ class AndroidTorPlugin extends TorPlugin {
 				appContext.getDir("tor", MODE_PRIVATE));
 		this.appContext = appContext;
 		PowerManager pm = (PowerManager)
-				requireNonNull(appContext.getSystemService(POWER_SERVICE));
+				appContext.getSystemService(POWER_SERVICE);
+		if (pm == null) throw new AssertionError();
 		wakeLock = new RenewableWakeLock(pm, scheduler, PARTIAL_WAKE_LOCK,
 				WAKE_LOCK_TAG, 1, MINUTES);
 	}

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPluginFactory.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.plugin.tor;
 
 import android.content.Context;
+import android.os.Build;
 
 import org.briarproject.bramble.api.battery.BatteryManager;
 import org.briarproject.bramble.api.event.EventBus;
@@ -25,15 +26,12 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.Immutable;
 import javax.net.SocketFactory;
 
-import static android.os.Build.VERSION.SDK_INT;
-import static java.util.logging.Logger.getLogger;
-
 @Immutable
 @NotNullByDefault
 public class AndroidTorPluginFactory implements DuplexPluginFactory {
 
 	private static final Logger LOG =
-			getLogger(AndroidTorPluginFactory.class.getName());
+			Logger.getLogger(AndroidTorPluginFactory.class.getName());
 
 	private static final int MAX_LATENCY = 30 * 1000; // 30 seconds
 	private static final int MAX_IDLE_TIME = 30 * 1000; // 30 seconds
@@ -104,7 +102,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 			return null;
 		}
 		// Use position-independent executable for SDK >= 16
-		if (SDK_INT >= 16) architecture += "_pie";
+		if (Build.VERSION.SDK_INT >= 16) architecture += "_pie";
 
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidLocationUtils.java

@@ -15,13 +15,12 @@ import java.util.logging.Logger;
 import javax.inject.Inject;
 
 import static android.content.Context.TELEPHONY_SERVICE;
-import static java.util.logging.Logger.getLogger;
 
 @NotNullByDefault
 class AndroidLocationUtils implements LocationUtils {
 
 	private static final Logger LOG =
-			getLogger(AndroidLocationUtils.class.getName());
+			Logger.getLogger(AndroidLocationUtils.class.getName());
 
 	private final Context appContext;
 
@@ -60,14 +59,14 @@ class AndroidLocationUtils implements LocationUtils {
 	}
 
 	private String getCountryFromPhoneNetwork() {
-		TelephonyManager tm = (TelephonyManager)
-				appContext.getSystemService(TELEPHONY_SERVICE);
-		return tm == null ? "" : tm.getNetworkCountryIso();
+		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
+		TelephonyManager tm = (TelephonyManager) o;
+		return tm.getNetworkCountryIso();
 	}
 
 	private String getCountryFromSimCard() {
-		TelephonyManager tm = (TelephonyManager)
-				appContext.getSystemService(TELEPHONY_SERVICE);
-		return tm == null ? "" : tm.getSimCountryIso();
+		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
+		TelephonyManager tm = (TelephonyManager) o;
+		return tm.getSimCountryIso();
 	}
 }

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSecureRandomProvider.java

@@ -8,6 +8,7 @@ import android.content.ContentResolver;
 import android.content.Context;
 import android.net.wifi.WifiConfiguration;
 import android.net.wifi.WifiManager;
+import android.os.Build;
 import android.os.Parcel;
 import android.os.StrictMode;
 import android.provider.Settings;
@@ -22,9 +23,6 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static android.content.Context.WIFI_SERVICE;
-import static android.os.Build.FINGERPRINT;
-import static android.os.Build.SERIAL;
-import static android.os.Build.VERSION.SDK_INT;
 import static android.provider.Settings.Secure.ANDROID_ID;
 
 @Immutable
@@ -47,8 +45,8 @@ class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 		out.writeInt(android.os.Process.myPid());
 		out.writeInt(android.os.Process.myTid());
 		out.writeInt(android.os.Process.myUid());
-		if (FINGERPRINT != null) out.writeUTF(FINGERPRINT);
-		if (SERIAL != null) out.writeUTF(SERIAL);
+		if (Build.FINGERPRINT != null) out.writeUTF(Build.FINGERPRINT);
+		if (Build.SERIAL != null) out.writeUTF(Build.SERIAL);
 		ContentResolver contentResolver = appContext.getContentResolver();
 		String id = Settings.Secure.getString(contentResolver, ANDROID_ID);
 		if (id != null) out.writeUTF(id);
@@ -76,13 +74,15 @@ class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 		// Silence strict mode
 		StrictMode.ThreadPolicy tp = StrictMode.allowThreadDiskWrites();
 		super.writeSeed();
-		if (SDK_INT >= 16 && SDK_INT <= 18) applyOpenSslFix();
+		if (Build.VERSION.SDK_INT >= 16 && Build.VERSION.SDK_INT <= 18)
+			applyOpenSslFix();
 		StrictMode.setThreadPolicy(tp);
 	}
 
 	// Based on https://android-developers.googleblog.com/2013/08/some-securerandom-thoughts.html
 	private void applyOpenSslFix() {
-		byte[] seed = new UnixSecureRandomSpi().engineGenerateSeed(SEED_LENGTH);
+		byte[] seed = new UnixSecureRandomSpi().engineGenerateSeed(
+				SEED_LENGTH);
 		try {
 			// Seed the OpenSSL PRNG
 			Class.forName("org.apache.harmony.xnet.provider.jsse.NativeCrypto")

bramble-android/src/main/java/org/briarproject/bramble/util/AndroidUtils.java

@@ -3,20 +3,17 @@ package org.briarproject.bramble.util;
 import android.annotation.SuppressLint;
 import android.bluetooth.BluetoothAdapter;
 import android.content.Context;
+import android.os.Build;
 import android.provider.Settings;
 
 import java.io.File;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 
 import static android.content.Context.MODE_PRIVATE;
-import static android.os.Build.CPU_ABI;
-import static android.os.Build.CPU_ABI2;
-import static android.os.Build.SUPPORTED_ABIS;
 import static android.os.Build.VERSION.SDK_INT;
-import static java.util.Arrays.asList;
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 public class AndroidUtils {
 
@@ -25,13 +22,14 @@ public class AndroidUtils {
 
 	private static final String STORED_REPORTS = "dev-reports";
 
+	@SuppressWarnings("deprecation")
 	public static Collection<String> getSupportedArchitectures() {
 		List<String> abis = new ArrayList<>();
 		if (SDK_INT >= 21) {
-			abis.addAll(asList(SUPPORTED_ABIS));
+			abis.addAll(Arrays.asList(Build.SUPPORTED_ABIS));
 		} else {
-			abis.add(CPU_ABI);
-			if (CPU_ABI2 != null) abis.add(CPU_ABI2);
+			abis.add(Build.CPU_ABI);
+			if (Build.CPU_ABI2 != null) abis.add(Build.CPU_ABI2);
 		}
 		return abis;
 	}
@@ -51,7 +49,7 @@ public class AndroidUtils {
 	}
 
 	private static boolean isValidBluetoothAddress(String address) {
-		return !isNullOrEmpty(address)
+		return !StringUtils.isNullOrEmpty(address)
 				&& BluetoothAdapter.checkBluetoothAddress(address)
 				&& !address.equals(FAKE_BLUETOOTH_ADDRESS);
 	}

bramble-android/src/main/java/org/briarproject/bramble/util/RenewableWakeLock.java

@@ -10,19 +10,17 @@ import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
 
 @ThreadSafe
 @NotNullByDefault
 public class RenewableWakeLock {
 
 	private static final Logger LOG =
-			getLogger(RenewableWakeLock.class.getName());
+			Logger.getLogger(RenewableWakeLock.class.getName());
 
 	/**
 	 * Automatically release the lock this many milliseconds after it's due
@@ -38,12 +36,10 @@ public class RenewableWakeLock {
 	private final Runnable renewTask;
 
 	private final Object lock = new Object();
-	@GuardedBy("lock")
 	@Nullable
-	private PowerManager.WakeLock wakeLock;
-	@GuardedBy("lock")
+	private PowerManager.WakeLock wakeLock; // Locking: lock
 	@Nullable
-	private ScheduledFuture future;
+	private ScheduledFuture future; // Locking: lock
 
 	public RenewableWakeLock(PowerManager powerManager,
 			ScheduledExecutorService scheduler, int levelAndFlags, String tag,

bramble-api/src/main/java/org/briarproject/bramble/api/Bytes.java

@@ -1,14 +1,13 @@
 package org.briarproject.bramble.api;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.StringUtils;
 
 import java.util.Arrays;
 import java.util.Comparator;
 
 import javax.annotation.concurrent.ThreadSafe;
 
-import static org.briarproject.bramble.util.StringUtils.toHexString;
-
 /**
  * A wrapper around a byte array, to allow it to be stored in maps etc.
  */
@@ -57,7 +56,8 @@ public class Bytes implements Comparable<Bytes> {
 
 	@Override
 	public String toString() {
-		return getClass().getSimpleName() + "(" + toHexString(getBytes()) + ")";
+		return getClass().getSimpleName() +
+				"(" + StringUtils.toHexString(getBytes()) + ")";
 	}
 
 	public static class BytesComparator implements Comparator<Bytes> {

bramble-api/src/main/java/org/briarproject/bramble/api/Multiset.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.api;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.NoSuchElementException;
@@ -9,8 +10,6 @@ import java.util.Set;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.util.Collections.unmodifiableSet;
-
 @NotThreadSafe
 @NotNullByDefault
 public class Multiset<T> {
@@ -97,6 +96,6 @@ public class Multiset<T> {
 	 * is unmodifiable.
 	 */
 	public Set<T> keySet() {
-		return unmodifiableSet(map.keySet());
+		return Collections.unmodifiableSet(map.keySet());
 	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/client/BdfMessageContext.java

@@ -5,11 +5,10 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 
 import java.util.Collection;
+import java.util.Collections;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.Collections.emptyList;
-
 @Immutable
 @NotNullByDefault
 public class BdfMessageContext {
@@ -24,7 +23,7 @@ public class BdfMessageContext {
 	}
 
 	public BdfMessageContext(BdfDictionary dictionary) {
-		this(dictionary, emptyList());
+		this(dictionary, Collections.emptyList());
 	}
 
 	public BdfDictionary getDictionary() {

bramble-api/src/main/java/org/briarproject/bramble/api/client/BdfMessageValidator.java

@@ -16,7 +16,6 @@ import java.util.logging.Logger;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_CLOCK_DIFFERENCE;
 
 @Immutable
@@ -24,7 +23,7 @@ import static org.briarproject.bramble.api.transport.TransportConstants.MAX_CLOC
 public abstract class BdfMessageValidator implements MessageValidator {
 
 	protected static final Logger LOG =
-			getLogger(BdfMessageValidator.class.getName());
+			Logger.getLogger(BdfMessageValidator.class.getName());
 
 	protected final ClientHelper clientHelper;
 	protected final MetadataEncoder metadataEncoder;

bramble-api/src/main/java/org/briarproject/bramble/api/data/BdfDictionary.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.Bytes;
 import org.briarproject.bramble.api.FormatException;
 
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.TreeMap;
 
 import javax.annotation.Nullable;
@@ -23,9 +24,9 @@ public class BdfDictionary extends TreeMap<String, Object> {
 	 * );
 	 * </pre>
 	 */
-	public static BdfDictionary of(BdfEntry... entries) {
+	public static BdfDictionary of(Entry<String, ?>... entries) {
 		BdfDictionary d = new BdfDictionary();
-		for (BdfEntry e : entries) d.put(e.getKey(), e.getValue());
+		for (Entry<String, ?> e : entries) d.put(e.getKey(), e.getValue());
 		return d;
 	}
 

bramble-api/src/main/java/org/briarproject/bramble/api/data/BdfList.java

@@ -4,12 +4,12 @@ import org.briarproject.bramble.api.Bytes;
 import org.briarproject.bramble.api.FormatException;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.util.Arrays.asList;
 import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
 
 @NotThreadSafe
@@ -22,7 +22,7 @@ public class BdfList extends ArrayList<Object> {
 	 * </pre>
 	 */
 	public static BdfList of(Object... items) {
-		return new BdfList(asList(items));
+		return new BdfList(Arrays.asList(items));
 	}
 
 	public BdfList() {
@@ -33,7 +33,6 @@ public class BdfList extends ArrayList<Object> {
 		super(items);
 	}
 
-	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	private boolean isInRange(int index) {
 		return index >= 0 && index < size();
 	}

bramble-api/src/main/java/org/briarproject/bramble/api/db/Transaction.java

@@ -3,12 +3,11 @@ package org.briarproject.bramble.api.db;
 import org.briarproject.bramble.api.event.Event;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.util.Collections.emptyList;
-
 /**
  * A wrapper around a database transaction. Transactions are not thread-safe.
  */
@@ -54,7 +53,7 @@ public class Transaction {
 	 * Returns any events attached to the transaction.
 	 */
 	public List<Event> getEvents() {
-		if (events == null) return emptyList();
+		if (events == null) return Collections.emptyList();
 		return events;
 	}
 

bramble-api/src/main/java/org/briarproject/bramble/api/identity/Author.java

@@ -2,12 +2,12 @@ package org.briarproject.bramble.api.identity;
 
 import org.briarproject.bramble.api.Nameable;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.StringUtils;
 
 import javax.annotation.concurrent.Immutable;
 
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
 
 /**
  * A pseudonym for a user.
@@ -28,7 +28,7 @@ public class Author implements Nameable {
 
 	public Author(AuthorId id, int formatVersion, String name,
 			byte[] publicKey) {
-		int nameLength = toUtf8(name).length;
+		int nameLength = StringUtils.toUtf8(name).length;
 		if (nameLength == 0 || nameLength > MAX_AUTHOR_NAME_LENGTH)
 			throw new IllegalArgumentException();
 		if (publicKey.length == 0 || publicKey.length > MAX_PUBLIC_KEY_LENGTH)

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/TorConstants.java

@@ -16,7 +16,6 @@ public interface TorConstants {
 	String PREF_TOR_NETWORK = "network2";
 	String PREF_TOR_PORT = "port";
 	String PREF_TOR_MOBILE = "useMobileData";
-	String PREF_TOR_ONLY_WHEN_CHARGING = "onlyWhenCharging";
 
 	int PREF_TOR_NETWORK_AUTOMATIC = 0;
 	int PREF_TOR_NETWORK_WITHOUT_BRIDGES = 1;

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/TransportId.java

@@ -1,6 +1,6 @@
 package org.briarproject.bramble.api.plugin;
 
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
+import org.briarproject.bramble.util.StringUtils;
 
 /**
  * Type-safe wrapper for a namespaced string that uniquely identifies a
@@ -11,12 +11,12 @@ public class TransportId {
 	/**
 	 * The maximum length of a transport identifier in UTF-8 bytes.
 	 */
-	public static final int MAX_TRANSPORT_ID_LENGTH = 100;
+	public static int MAX_TRANSPORT_ID_LENGTH = 100;
 
 	private final String id;
 
 	public TransportId(String id) {
-		int length = toUtf8(id).length;
+		int length = StringUtils.toUtf8(id).length;
 		if (length == 0 || length > MAX_TRANSPORT_ID_LENGTH)
 			throw new IllegalArgumentException();
 		this.id = id;

bramble-api/src/main/java/org/briarproject/bramble/api/sync/ClientId.java

@@ -1,11 +1,10 @@
 package org.briarproject.bramble.api.sync;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.StringUtils;
 
 import javax.annotation.concurrent.Immutable;
 
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
-
 /**
  * Type-safe wrapper for a namespaced string that uniquely identifies a sync
  * client.
@@ -17,12 +16,12 @@ public class ClientId implements Comparable<ClientId> {
 	/**
 	 * The maximum length of a client identifier in UTF-8 bytes.
 	 */
-	public static final int MAX_CLIENT_ID_LENGTH = 100;
+	public static int MAX_CLIENT_ID_LENGTH = 100;
 
 	private final String id;
 
 	public ClientId(String id) {
-		int length = toUtf8(id).length;
+		int length = StringUtils.toUtf8(id).length;
 		if (length == 0 || length > MAX_CLIENT_ID_LENGTH)
 			throw new IllegalArgumentException();
 		this.id = id;

bramble-api/src/main/java/org/briarproject/bramble/api/sync/MessageContext.java

@@ -4,11 +4,10 @@ import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.util.Collection;
+import java.util.Collections;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.util.Collections.emptyList;
-
 @Immutable
 @NotNullByDefault
 public class MessageContext {
@@ -23,7 +22,7 @@ public class MessageContext {
 	}
 
 	public MessageContext(Metadata metadata) {
-		this(metadata, emptyList());
+		this(metadata, Collections.emptyList());
 	}
 
 	public Metadata getMetadata() {

bramble-api/src/main/java/org/briarproject/bramble/util/IoUtils.java

@@ -16,13 +16,12 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
 public class IoUtils {
 
-	private static final Logger LOG = getLogger(IoUtils.class.getName());
+	private static final Logger LOG = Logger.getLogger(IoUtils.class.getName());
 
 	public static void deleteFileOrDir(File f) {
 		if (f.isFile()) {

bramble-api/src/main/java/org/briarproject/bramble/util/ValidationUtils.java

@@ -7,15 +7,13 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import javax.annotation.Nullable;
 
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
-
 @NotNullByDefault
 public class ValidationUtils {
 
 	public static void checkLength(@Nullable String s, int minLength,
 			int maxLength) throws FormatException {
 		if (s != null) {
-			int length = toUtf8(s).length;
+			int length = StringUtils.toUtf8(s).length;
 			if (length < minLength) throw new FormatException();
 			if (length > maxLength) throw new FormatException();
 		}
@@ -23,7 +21,7 @@ public class ValidationUtils {
 
 	public static void checkLength(@Nullable String s, int length)
 			throws FormatException {
-		if (s != null && toUtf8(s).length != length)
+		if (s != null && StringUtils.toUtf8(s).length != length)
 			throw new FormatException();
 	}
 

bramble-api/src/test/java/org/briarproject/bramble/api/data/BdfDictionaryTest.java

@@ -8,7 +8,6 @@ import java.util.Collections;
 import java.util.Iterator;
 import java.util.Map.Entry;
 
-import static java.util.Collections.singletonMap;
 import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
@@ -20,15 +19,15 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	public void testConstructors() {
 		assertEquals(Collections.<String, Object>emptyMap(),
 				new BdfDictionary());
-		assertEquals(singletonMap("foo", NULL_VALUE),
-				new BdfDictionary(singletonMap("foo", NULL_VALUE)));
+		assertEquals(Collections.singletonMap("foo", NULL_VALUE),
+				new BdfDictionary(Collections.singletonMap("foo", NULL_VALUE)));
 	}
 
 	@Test
 	public void testFactoryMethod() {
 		assertEquals(Collections.<String, Object>emptyMap(),
 				BdfDictionary.of());
-		assertEquals(singletonMap("foo", NULL_VALUE),
+		assertEquals(Collections.singletonMap("foo", NULL_VALUE),
 				BdfDictionary.of(new BdfEntry("foo", NULL_VALUE)));
 	}
 
@@ -68,7 +67,7 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testKeySetIteratorIsOrderedByKeys() {
+	public void testKeySetIteratorIsOrderedByKeys() throws Exception {
 		BdfDictionary d = new BdfDictionary();
 		d.put("a", 1);
 		d.put("d", 4);
@@ -87,7 +86,7 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testValuesIteratorIsOrderedByKeys() {
+	public void testValuesIteratorIsOrderedByKeys() throws Exception {
 		BdfDictionary d = new BdfDictionary();
 		d.put("a", 1);
 		d.put("d", 4);
@@ -106,7 +105,7 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testEntrySetIteratorIsOrderedByKeys() {
+	public void testEntrySetIteratorIsOrderedByKeys() throws Exception {
 		BdfDictionary d = new BdfDictionary();
 		d.put("a", 1);
 		d.put("d", 4);

bramble-api/src/test/java/org/briarproject/bramble/api/data/BdfListTest.java

@@ -5,31 +5,26 @@ import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.junit.Test;
 
-import java.util.Random;
+import java.util.Arrays;
+import java.util.Collections;
 
-import static java.util.Arrays.asList;
-import static java.util.Collections.emptyList;
 import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
-import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
-import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 
 public class BdfListTest extends BrambleTestCase {
 
-	private final Random random = new Random();
-
 	@Test
 	public void testConstructors() {
-		assertEquals(emptyList(), new BdfList());
-		assertEquals(asList(1, 2, NULL_VALUE),
-				new BdfList(asList(1, 2, NULL_VALUE)));
+		assertEquals(Collections.emptyList(), new BdfList());
+		assertEquals(Arrays.asList(1, 2, NULL_VALUE),
+				new BdfList(Arrays.asList(1, 2, NULL_VALUE)));
 	}
 
 	@Test
 	public void testFactoryMethod() {
-		assertEquals(emptyList(), BdfList.of());
-		assertEquals(asList(1, 2, NULL_VALUE),
+		assertEquals(Collections.emptyList(), BdfList.of());
+		assertEquals(Arrays.asList(1, 2, NULL_VALUE),
 				BdfList.of(1, 2, NULL_VALUE));
 	}
 
@@ -69,21 +64,22 @@ public class BdfListTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testIndexOutOfBoundsReturnsDefaultValue() {
+	@SuppressWarnings("ConstantConditions")
+	public void testIndexOutOfBoundsReturnsDefaultValue() throws Exception {
 		BdfList list = BdfList.of(1, 2, 3);
-		boolean defaultBoolean = random.nextBoolean();
+		boolean defaultBoolean = true;
 		assertEquals(defaultBoolean, list.getBoolean(-1, defaultBoolean));
 		assertEquals(defaultBoolean, list.getBoolean(3, defaultBoolean));
-		Long defaultLong = random.nextLong();
+		Long defaultLong = 123L;
 		assertEquals(defaultLong, list.getLong(-1, defaultLong));
 		assertEquals(defaultLong, list.getLong(3, defaultLong));
-		Double defaultDouble = random.nextDouble();
+		Double defaultDouble = 1.23;
 		assertEquals(defaultDouble, list.getDouble(-1, defaultDouble));
 		assertEquals(defaultDouble, list.getDouble(3, defaultDouble));
-		String defaultString = getRandomString(123);
+		String defaultString = "123";
 		assertEquals(defaultString, list.getString(-1, defaultString));
 		assertEquals(defaultString, list.getString(3, defaultString));
-		byte[] defaultBytes = getRandomBytes(123);
+		byte[] defaultBytes = new byte[] {1, 2, 3};
 		assertArrayEquals(defaultBytes, list.getRaw(-1, defaultBytes));
 		assertArrayEquals(defaultBytes, list.getRaw(3, defaultBytes));
 		BdfList defaultList = BdfList.of(1, 2, 3);
@@ -99,17 +95,18 @@ public class BdfListTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testWrongTypeReturnsDefaultValue() {
+	@SuppressWarnings("ConstantConditions")
+	public void testWrongTypeReturnsDefaultValue() throws Exception {
 		BdfList list = BdfList.of(1, 2, 3, true);
-		boolean defaultBoolean = random.nextBoolean();
+		boolean defaultBoolean = true;
 		assertEquals(defaultBoolean, list.getBoolean(0, defaultBoolean));
-		Long defaultLong = random.nextLong();
+		Long defaultLong = 123L;
 		assertEquals(defaultLong, list.getLong(3, defaultLong));
-		Double defaultDouble = random.nextDouble();
+		Double defaultDouble = 1.23;
 		assertEquals(defaultDouble, list.getDouble(0, defaultDouble));
-		String defaultString = getRandomString(123);
+		String defaultString = "123";
 		assertEquals(defaultString, list.getString(0, defaultString));
-		byte[] defaultBytes = getRandomBytes(123);
+		byte[] defaultBytes = new byte[] {1, 2, 3};
 		assertArrayEquals(defaultBytes, list.getRaw(0, defaultBytes));
 		BdfList defaultList = BdfList.of(1, 2, 3);
 		assertEquals(defaultList, list.getList(0, defaultList));

bramble-api/src/test/java/org/briarproject/bramble/test/TestUtils.java

@@ -12,10 +12,12 @@ import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.util.IoUtils;
 
 import java.io.File;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -23,7 +25,6 @@ import java.util.Random;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import static java.util.Arrays.asList;
-import static java.util.Collections.sort;
 import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
@@ -32,7 +33,6 @@ import static org.briarproject.bramble.api.properties.TransportPropertyConstants
 import static org.briarproject.bramble.api.sync.ClientId.MAX_CLIENT_ID_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
-import static org.briarproject.bramble.util.IoUtils.deleteFileOrDir;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
 
 public class TestUtils {
@@ -48,10 +48,8 @@ public class TestUtils {
 	}
 
 	public static void deleteTestDirectory(File testDir) {
-		deleteFileOrDir(testDir);
-		// Delete parent directory only if it's empty
-		//noinspection ResultOfMethodCallIgnored
-		testDir.getParentFile().delete();
+		IoUtils.deleteFileOrDir(testDir);
+		testDir.getParentFile().delete(); // Delete if empty
 	}
 
 	public static byte[] getRandomBytes(int length) {
@@ -147,7 +145,7 @@ public class TestUtils {
 		if (size == 0) throw new IllegalArgumentException();
 		List<Double> sorted = new ArrayList<>(size);
 		for (Number n : samples) sorted.add(n.doubleValue());
-		sort(sorted);
+		Collections.sort(sorted);
 		if (size % 2 == 1) return sorted.get(size / 2);
 		double low = sorted.get(size / 2 - 1), high = sorted.get(size / 2);
 		return (low + high) / 2;

bramble-core/src/main/java/org/briarproject/bramble/PoliteExecutor.java

@@ -10,7 +10,6 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.GuardedBy;
 
 import static java.util.logging.Level.FINE;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.now;
 
 /**
@@ -43,7 +42,7 @@ public class PoliteExecutor implements Executor {
 			int maxConcurrentTasks) {
 		this.delegate = delegate;
 		this.maxConcurrentTasks = maxConcurrentTasks;
-		log = getLogger(tag);
+		log = Logger.getLogger(tag);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/TimeLoggingExecutor.java

@@ -9,7 +9,6 @@ import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.FINE;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.now;
 
 @NotNullByDefault
@@ -23,7 +22,7 @@ public class TimeLoggingExecutor extends ThreadPoolExecutor {
 			RejectedExecutionHandler handler) {
 		super(corePoolSize, maxPoolSize, keepAliveTime, unit, workQueue,
 				handler);
-		log = getLogger(tag);
+		log = Logger.getLogger(tag);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/account/AccountManagerImpl.java

@@ -6,7 +6,9 @@ import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.util.IoUtils;
 
 import java.io.BufferedReader;
 import java.io.File;
@@ -17,21 +19,19 @@ import java.io.InputStreamReader;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.IoUtils.deleteFileOrDir;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.fromHexString;
 import static org.briarproject.bramble.util.StringUtils.toHexString;
 
-@NotNullByDefault
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 class AccountManagerImpl implements AccountManager {
 
 	private static final Logger LOG =
-			getLogger(AccountManagerImpl.class.getName());
+			Logger.getLogger(AccountManagerImpl.class.getName());
 
 	private static final String DB_KEY_FILENAME = "db.key";
 	private static final String DB_KEY_BACKUP_FILENAME = "db.key.bak";
@@ -68,7 +68,7 @@ class AccountManagerImpl implements AccountManager {
 		return databaseKey;
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	@Nullable
 	protected String loadEncryptedDatabaseKey() {
 		String key = readDbKeyFromFile(dbKeyFile);
@@ -83,7 +83,7 @@ class AccountManagerImpl implements AccountManager {
 		return key;
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	@Nullable
 	private String readDbKeyFromFile(File f) {
 		if (!f.exists()) {
@@ -102,8 +102,8 @@ class AccountManagerImpl implements AccountManager {
 		}
 	}
 
-	@GuardedBy("stateChangeLock")
-	boolean storeEncryptedDatabaseKey(String hex) {
+	// Locking: stateChangeLock
+	protected boolean storeEncryptedDatabaseKey(String hex) {
 		LOG.info("Storing database key in file");
 		// Create the directory if necessary
 		if (databaseConfig.getDatabaseKeyDirectory().mkdirs())
@@ -140,7 +140,7 @@ class AccountManagerImpl implements AccountManager {
 		}
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	private void writeDbKeyToFile(String key, File f) throws IOException {
 		FileOutputStream out = new FileOutputStream(f);
 		out.write(key.getBytes("UTF-8"));
@@ -170,7 +170,7 @@ class AccountManagerImpl implements AccountManager {
 		}
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	private boolean encryptAndStoreDatabaseKey(SecretKey key, String password) {
 		byte[] plaintext = key.getBytes();
 		byte[] ciphertext = crypto.encryptWithPassword(plaintext, password);
@@ -181,8 +181,8 @@ class AccountManagerImpl implements AccountManager {
 	public void deleteAccount() {
 		synchronized (stateChangeLock) {
 			LOG.info("Deleting account");
-			deleteFileOrDir(databaseConfig.getDatabaseKeyDirectory());
-			deleteFileOrDir(databaseConfig.getDatabaseDirectory());
+			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseKeyDirectory());
+			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseDirectory());
 			databaseKey = null;
 		}
 	}
@@ -197,7 +197,7 @@ class AccountManagerImpl implements AccountManager {
 		}
 	}
 
-	@GuardedBy("stateChangeLock")
+	// Locking: stateChangeLock
 	@Nullable
 	private SecretKey loadAndDecryptDatabaseKey(String password) {
 		String hex = loadEncryptedDatabaseKey();

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactExchangeTaskImpl.java

@@ -43,7 +43,6 @@ import java.util.logging.Logger;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.contact.RecordTypes.CONTACT_INFO;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -55,7 +54,7 @@ import static org.briarproject.bramble.util.ValidationUtils.checkSize;
 class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 
 	private static final Logger LOG =
-			getLogger(ContactExchangeTaskImpl.class.getName());
+			Logger.getLogger(ContactExchangeTaskImpl.class.getName());
 
 	private static final String SIGNING_LABEL_EXCHANGE =
 			"org.briarproject.briar.contact/EXCHANGE";
@@ -191,7 +190,6 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 			streamWriter.sendEndOfStream();
 			// Skip any remaining records from the incoming stream
 			try {
-				//noinspection InfiniteLoopStatement
 				while (true) recordReader.readRecord();
 			} catch (EOFException expected) {
 				LOG.info("End of stream");

bramble-core/src/main/java/org/briarproject/bramble/crypto/AsciiArmour.java

@@ -2,20 +2,18 @@ package org.briarproject.bramble.crypto;
 
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import static org.briarproject.bramble.util.StringUtils.fromHexString;
-import static org.briarproject.bramble.util.StringUtils.toHexString;
+import org.briarproject.bramble.util.StringUtils;
 
 @NotNullByDefault
 class AsciiArmour {
 
 	static String wrap(byte[] b, int lineLength) {
-		String wrapped = toHexString(b);
+		String wrapped = StringUtils.toHexString(b);
 		StringBuilder s = new StringBuilder();
 		int length = wrapped.length();
 		for (int i = 0; i < length; i += lineLength) {
 			int end = Math.min(i + lineLength, length);
-			s.append(wrapped, i, end);
+			s.append(wrapped.substring(i, end));
 			s.append("\r\n");
 		}
 		return s.toString();
@@ -23,7 +21,7 @@ class AsciiArmour {
 
 	static byte[] unwrap(String s) throws FormatException {
 		try {
-			return fromHexString(s.replaceAll("[^0-9a-fA-F]", ""));
+			return StringUtils.fromHexString(s.replaceAll("[^0-9a-fA-F]", ""));
 		} catch (IllegalArgumentException e) {
 			throw new FormatException();
 		}

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java

@@ -12,6 +12,8 @@ import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.SecureRandomProvider;
+import org.briarproject.bramble.util.ByteUtils;
+import org.briarproject.bramble.util.StringUtils;
 import org.spongycastle.crypto.CryptoException;
 import org.spongycastle.crypto.Digest;
 import org.spongycastle.crypto.digests.Blake2bDigest;
@@ -28,21 +30,16 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import static java.lang.System.arraycopy;
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.readUint32;
-import static org.briarproject.bramble.util.ByteUtils.writeUint32;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
 
 @NotNullByDefault
 class CryptoComponentImpl implements CryptoComponent {
 
 	private static final Logger LOG =
-			getLogger(CryptoComponentImpl.class.getName());
+			Logger.getLogger(CryptoComponentImpl.class.getName());
 
 	private static final int SIGNATURE_KEY_PAIR_BITS = 256;
 	private static final int STORAGE_IV_BYTES = 24; // 196 bits
@@ -191,7 +188,7 @@ class CryptoComponentImpl implements CryptoComponent {
 		PrivateKey ourPriv = ourKeyPair.getPrivate();
 		byte[][] hashInputs = new byte[inputs.length + 1][];
 		hashInputs[0] = performRawKeyAgreement(ourPriv, theirPublicKey);
-		arraycopy(inputs, 0, hashInputs, 1, inputs.length);
+		System.arraycopy(inputs, 0, hashInputs, 1, inputs.length);
 		byte[] hash = hash(label, hashInputs);
 		if (hash.length != SecretKey.LENGTH) throw new IllegalStateException();
 		return new SecretKey(hash);
@@ -219,26 +216,26 @@ class CryptoComponentImpl implements CryptoComponent {
 
 	private void updateSignature(Signature signature, String label,
 			byte[] toSign) throws GeneralSecurityException {
-		byte[] labelBytes = toUtf8(label);
+		byte[] labelBytes = StringUtils.toUtf8(label);
 		byte[] length = new byte[INT_32_BYTES];
-		writeUint32(labelBytes.length, length, 0);
+		ByteUtils.writeUint32(labelBytes.length, length, 0);
 		signature.update(length);
 		signature.update(labelBytes);
-		writeUint32(toSign.length, length, 0);
+		ByteUtils.writeUint32(toSign.length, length, 0);
 		signature.update(length);
 		signature.update(toSign);
 	}
 
 	@Override
 	public byte[] hash(String label, byte[]... inputs) {
-		byte[] labelBytes = toUtf8(label);
+		byte[] labelBytes = StringUtils.toUtf8(label);
 		Digest digest = new Blake2bDigest(256);
 		byte[] length = new byte[INT_32_BYTES];
-		writeUint32(labelBytes.length, length, 0);
+		ByteUtils.writeUint32(labelBytes.length, length, 0);
 		digest.update(length, 0, length.length);
 		digest.update(labelBytes, 0, labelBytes.length);
 		for (byte[] input : inputs) {
-			writeUint32(input.length, length, 0);
+			ByteUtils.writeUint32(input.length, length, 0);
 			digest.update(length, 0, length.length);
 			digest.update(input, 0, input.length);
 		}
@@ -249,14 +246,14 @@ class CryptoComponentImpl implements CryptoComponent {
 
 	@Override
 	public byte[] mac(String label, SecretKey macKey, byte[]... inputs) {
-		byte[] labelBytes = toUtf8(label);
+		byte[] labelBytes = StringUtils.toUtf8(label);
 		Digest mac = new Blake2bDigest(macKey.getBytes(), 32, null, null);
 		byte[] length = new byte[INT_32_BYTES];
-		writeUint32(labelBytes.length, length, 0);
+		ByteUtils.writeUint32(labelBytes.length, length, 0);
 		mac.update(length, 0, length.length);
 		mac.update(labelBytes, 0, labelBytes.length);
 		for (byte[] input : inputs) {
-			writeUint32(input.length, length, 0);
+			ByteUtils.writeUint32(input.length, length, 0);
 			mac.update(length, 0, length.length);
 			mac.update(input, 0, input.length);
 		}
@@ -300,13 +297,13 @@ class CryptoComponentImpl implements CryptoComponent {
 		output[outputOff] = PBKDF_FORMAT_SCRYPT;
 		outputOff++;
 		// Salt
-		arraycopy(salt, 0, output, outputOff, salt.length);
+		System.arraycopy(salt, 0, output, outputOff, salt.length);
 		outputOff += salt.length;
 		// Cost parameter
-		writeUint32(cost, output, outputOff);
+		ByteUtils.writeUint32(cost, output, outputOff);
 		outputOff += INT_32_BYTES;
 		// IV
-		arraycopy(iv, 0, output, outputOff, iv.length);
+		System.arraycopy(iv, 0, output, outputOff, iv.length);
 		outputOff += iv.length;
 		// Initialise the cipher and encrypt the plaintext
 		try {
@@ -336,16 +333,16 @@ class CryptoComponentImpl implements CryptoComponent {
 			return null; // Unknown format
 		// Salt
 		byte[] salt = new byte[PBKDF_SALT_BYTES];
-		arraycopy(input, inputOff, salt, 0, salt.length);
+		System.arraycopy(input, inputOff, salt, 0, salt.length);
 		inputOff += salt.length;
 		// Cost parameter
-		long cost = readUint32(input, inputOff);
+		long cost = ByteUtils.readUint32(input, inputOff);
 		inputOff += INT_32_BYTES;
 		if (cost < 2 || cost > Integer.MAX_VALUE)
 			return null; // Invalid cost parameter
 		// IV
 		byte[] iv = new byte[STORAGE_IV_BYTES];
-		arraycopy(input, inputOff, iv, 0, iv.length);
+		System.arraycopy(input, inputOff, iv, 0, iv.length);
 		inputOff += iv.length;
 		// Derive the key from the password
 		SecretKey key = passwordBasedKdf.deriveKey(password, salt, (int) cost);

bramble-core/src/main/java/org/briarproject/bramble/crypto/Curve25519KeyParser.java

@@ -7,8 +7,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.security.GeneralSecurityException;
 
-import static java.lang.System.arraycopy;
-
 @NotNullByDefault
 class Curve25519KeyParser implements KeyParser {
 
@@ -28,7 +26,7 @@ class Curve25519KeyParser implements KeyParser {
 
 	static byte[] clamp(byte[] b) {
 		byte[] clamped = new byte[32];
-		arraycopy(b, 0, clamped, 0, 32);
+		System.arraycopy(b, 0, clamped, 0, 32);
 		clamped[0] &= 248;
 		clamped[31] &= 127;
 		clamped[31] |= 64;

bramble-core/src/main/java/org/briarproject/bramble/crypto/FrameEncoder.java

@@ -1,15 +1,13 @@
 package org.briarproject.bramble.crypto;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.ByteUtils;
 
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_HEADER_PLAINTEXT_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_NONCE_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
 import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.readUint16;
-import static org.briarproject.bramble.util.ByteUtils.writeUint16;
-import static org.briarproject.bramble.util.ByteUtils.writeUint64;
 
 @NotNullByDefault
 class FrameEncoder {
@@ -18,7 +16,7 @@ class FrameEncoder {
 		if (dest.length < FRAME_NONCE_LENGTH)
 			throw new IllegalArgumentException();
 		if (frameNumber < 0) throw new IllegalArgumentException();
-		writeUint64(frameNumber, dest, 0);
+		ByteUtils.writeUint64(frameNumber, dest, 0);
 		if (header) dest[0] |= 0x80;
 		for (int i = INT_64_BYTES; i < FRAME_NONCE_LENGTH; i++) dest[i] = 0;
 	}
@@ -31,8 +29,8 @@ class FrameEncoder {
 		if (paddingLength < 0) throw new IllegalArgumentException();
 		if (payloadLength + paddingLength > MAX_PAYLOAD_LENGTH)
 			throw new IllegalArgumentException();
-		writeUint16(payloadLength, dest, 0);
-		writeUint16(paddingLength, dest, INT_16_BYTES);
+		ByteUtils.writeUint16(payloadLength, dest, 0);
+		ByteUtils.writeUint16(paddingLength, dest, INT_16_BYTES);
 		if (finalFrame) dest[0] |= 0x80;
 	}
 
@@ -45,12 +43,12 @@ class FrameEncoder {
 	static int getPayloadLength(byte[] header) {
 		if (header.length < FRAME_HEADER_PLAINTEXT_LENGTH)
 			throw new IllegalArgumentException();
-		return readUint16(header, 0) & 0x7FFF;
+		return ByteUtils.readUint16(header, 0) & 0x7FFF;
 	}
 
 	static int getPaddingLength(byte[] header) {
 		if (header.length < FRAME_HEADER_PLAINTEXT_LENGTH)
 			throw new IllegalArgumentException();
-		return readUint16(header, INT_16_BYTES);
+		return ByteUtils.readUint16(header, INT_16_BYTES);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/crypto/KeyAgreementCryptoImpl.java

@@ -8,7 +8,6 @@ import org.briarproject.bramble.api.crypto.SecretKey;
 
 import javax.inject.Inject;
 
-import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
 
 class KeyAgreementCryptoImpl implements KeyAgreementCrypto {
@@ -25,7 +24,7 @@ class KeyAgreementCryptoImpl implements KeyAgreementCrypto {
 		byte[] hash = crypto.hash(COMMIT_LABEL, publicKey.getEncoded());
 		// The output is the first COMMIT_LENGTH bytes of the hash
 		byte[] commitment = new byte[COMMIT_LENGTH];
-		arraycopy(hash, 0, commitment, 0, COMMIT_LENGTH);
+		System.arraycopy(hash, 0, commitment, 0, COMMIT_LENGTH);
 		return commitment;
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/crypto/MessageEncrypter.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.crypto.KeyParser;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.StringUtils;
 import org.spongycastle.asn1.teletrust.TeleTrusTNamedCurves;
 import org.spongycastle.asn1.x9.X9ECParameters;
 import org.spongycastle.crypto.AsymmetricCipherKeyPair;
@@ -44,9 +45,6 @@ import java.util.Scanner;
 
 import javax.annotation.concurrent.Immutable;
 
-import static org.briarproject.bramble.util.StringUtils.fromHexString;
-import static org.briarproject.bramble.util.StringUtils.toHexString;
-
 @Immutable
 @NotNullByDefault
 public class MessageEncrypter {
@@ -159,7 +157,6 @@ public class MessageEncrypter {
 			printUsage();
 			System.exit(1);
 		}
-		//noinspection IfCanBeSwitch
 		if (args[0].equals("generate")) {
 			if (args.length != 3) {
 				printUsage();
@@ -213,11 +210,11 @@ public class MessageEncrypter {
 		MessageEncrypter encrypter = new MessageEncrypter(random);
 		KeyPair keyPair = encrypter.generateKeyPair();
 		PrintStream out = new PrintStream(new FileOutputStream(publicKeyFile));
-		out.print(toHexString(keyPair.getPublic().getEncoded()));
+		out.print(StringUtils.toHexString(keyPair.getPublic().getEncoded()));
 		out.flush();
 		out.close();
 		out = new PrintStream(new FileOutputStream(privateKeyFile));
-		out.print(toHexString(keyPair.getPrivate().getEncoded()));
+		out.print(StringUtils.toHexString(keyPair.getPrivate().getEncoded()));
 		out.flush();
 		out.close();
 	}
@@ -226,7 +223,7 @@ public class MessageEncrypter {
 		SecureRandom random = new SecureRandom();
 		MessageEncrypter encrypter = new MessageEncrypter(random);
 		InputStream in = new FileInputStream(publicKeyFile);
-		byte[] keyBytes = fromHexString(readFully(in).trim());
+		byte[] keyBytes = StringUtils.fromHexString(readFully(in).trim());
 		PublicKey publicKey =
 				encrypter.getKeyParser().parsePublicKey(keyBytes);
 		String message = readFully(System.in);
@@ -239,7 +236,7 @@ public class MessageEncrypter {
 		SecureRandom random = new SecureRandom();
 		MessageEncrypter encrypter = new MessageEncrypter(random);
 		InputStream in = new FileInputStream(privateKeyFile);
-		byte[] keyBytes = fromHexString(readFully(in).trim());
+		byte[] keyBytes = StringUtils.fromHexString(readFully(in).trim());
 		PrivateKey privateKey =
 				encrypter.getKeyParser().parsePrivateKey(keyBytes);
 		byte[] ciphertext = AsciiArmour.unwrap(readFully(System.in));

bramble-core/src/main/java/org/briarproject/bramble/crypto/ScryptKdf.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.crypto;
 
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.util.StringUtils;
 import org.spongycastle.crypto.generators.SCrypt;
 
 import java.util.logging.Logger;
@@ -9,14 +10,13 @@ import java.util.logging.Logger;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
 
 class ScryptKdf implements PasswordBasedKdf {
 
-	private static final Logger LOG = getLogger(ScryptKdf.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(ScryptKdf.class.getName());
 
 	private static final int MIN_COST = 256; // Min parameter N
 	private static final int MAX_COST = 1024 * 1024; // Max parameter N
@@ -53,7 +53,7 @@ class ScryptKdf implements PasswordBasedKdf {
 	@Override
 	public SecretKey deriveKey(String password, byte[] salt, int cost) {
 		long start = now();
-		byte[] passwordBytes = toUtf8(password);
+		byte[] passwordBytes = StringUtils.toUtf8(password);
 		SecretKey k = new SecretKey(SCrypt.generate(passwordBytes, salt, cost,
 				BLOCK_SIZE, PARALLELIZATION, SecretKey.LENGTH));
 		logDuration(LOG, "Deriving key from password", start);

bramble-core/src/main/java/org/briarproject/bramble/crypto/Sec1KeyParser.java

@@ -16,8 +16,6 @@ import java.util.logging.Logger;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.lang.System.arraycopy;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
 
@@ -30,7 +28,8 @@ import static org.briarproject.bramble.util.LogUtils.now;
 @NotNullByDefault
 class Sec1KeyParser implements KeyParser {
 
-	private static final Logger LOG = getLogger(Sec1KeyParser.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(Sec1KeyParser.class.getName());
 
 	private final ECDomainParameters params;
 	private final BigInteger modulus;
@@ -57,12 +56,12 @@ class Sec1KeyParser implements KeyParser {
 		if (encodedKey[0] != 4) throw new GeneralSecurityException();
 		// The x co-ordinate must be >= 0 and < p
 		byte[] xBytes = new byte[bytesPerInt];
-		arraycopy(encodedKey, 1, xBytes, 0, bytesPerInt);
+		System.arraycopy(encodedKey, 1, xBytes, 0, bytesPerInt);
 		BigInteger x = new BigInteger(1, xBytes); // Positive signum
 		if (x.compareTo(modulus) >= 0) throw new GeneralSecurityException();
 		// The y co-ordinate must be >= 0 and < p
 		byte[] yBytes = new byte[bytesPerInt];
-		arraycopy(encodedKey, 1 + bytesPerInt, yBytes, 0, bytesPerInt);
+		System.arraycopy(encodedKey, 1 + bytesPerInt, yBytes, 0, bytesPerInt);
 		BigInteger y = new BigInteger(1, yBytes); // Positive signum
 		if (y.compareTo(modulus) >= 0) throw new GeneralSecurityException();
 		// Verify that y^2 == x^3 + ax + b (mod p)

bramble-core/src/main/java/org/briarproject/bramble/crypto/Sec1Utils.java

@@ -2,8 +2,6 @@ package org.briarproject.bramble.crypto;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
-import static java.lang.System.arraycopy;
-
 @NotNullByDefault
 class Sec1Utils {
 
@@ -12,10 +10,10 @@ class Sec1Utils {
 		if (src.length < destLen) {
 			int padding = destLen - src.length;
 			for (int i = destOff; i < destOff + padding; i++) dest[i] = 0;
-			arraycopy(src, 0, dest, destOff + padding, src.length);
+			System.arraycopy(src, 0, dest, destOff + padding, src.length);
 		} else {
 			int srcOff = src.length - destLen;
-			arraycopy(src, srcOff, dest, destOff, destLen);
+			System.arraycopy(src, srcOff, dest, destOff, destLen);
 		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamDecrypterImpl.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamDecrypter;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.ByteUtils;
 
 import java.io.EOFException;
 import java.io.IOException;
@@ -13,7 +14,6 @@ import java.security.GeneralSecurityException;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_HEADER_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_HEADER_PLAINTEXT_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_NONCE_LENGTH;
@@ -26,8 +26,6 @@ import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_H
 import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_PLAINTEXT_LENGTH;
 import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.readUint16;
-import static org.briarproject.bramble.util.ByteUtils.readUint64;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -132,7 +130,7 @@ class StreamDecrypterImpl implements StreamDecrypter {
 		}
 		// Extract the nonce
 		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
-		arraycopy(streamHeaderCiphertext, 0, streamHeaderNonce, 0,
+		System.arraycopy(streamHeaderCiphertext, 0, streamHeaderNonce, 0,
 				STREAM_HEADER_NONCE_LENGTH);
 		// Decrypt and authenticate the stream header
 		try {
@@ -147,16 +145,17 @@ class StreamDecrypterImpl implements StreamDecrypter {
 			throw new FormatException();
 		}
 		// Check the protocol version
-		int receivedProtocolVersion = readUint16(streamHeaderPlaintext, 0);
+		int receivedProtocolVersion =
+				ByteUtils.readUint16(streamHeaderPlaintext, 0);
 		if (receivedProtocolVersion != PROTOCOL_VERSION)
 			throw new FormatException();
 		// Check the stream number
-		long receivedStreamNumber = readUint64(streamHeaderPlaintext,
+		long receivedStreamNumber = ByteUtils.readUint64(streamHeaderPlaintext,
 				INT_16_BYTES);
 		if (receivedStreamNumber != streamNumber) throw new FormatException();
 		// Extract the frame key
 		byte[] frameKeyBytes = new byte[SecretKey.LENGTH];
-		arraycopy(streamHeaderPlaintext, INT_16_BYTES + INT_64_BYTES,
+		System.arraycopy(streamHeaderPlaintext, INT_16_BYTES + INT_64_BYTES,
 				frameKeyBytes, 0, SecretKey.LENGTH);
 		frameKey = new SecretKey(frameKeyBytes);
 	}

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamEncrypterImpl.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.crypto;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamEncrypter;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.ByteUtils;
 
 import java.io.IOException;
 import java.io.OutputStream;
@@ -11,7 +12,6 @@ import java.security.GeneralSecurityException;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_HEADER_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_HEADER_PLAINTEXT_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_NONCE_LENGTH;
@@ -24,8 +24,6 @@ import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_H
 import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_PLAINTEXT_LENGTH;
 import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.writeUint16;
-import static org.briarproject.bramble.util.ByteUtils.writeUint64;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -90,7 +88,7 @@ class StreamEncrypterImpl implements StreamEncrypter {
 			throw new RuntimeException(badCipher);
 		}
 		// Combine the payload and padding
-		arraycopy(payload, 0, framePlaintext, 0, payloadLength);
+		System.arraycopy(payload, 0, framePlaintext, 0, payloadLength);
 		for (int i = 0; i < paddingLength; i++)
 			framePlaintext[payloadLength + i] = 0;
 		// Encrypt and authenticate the payload and padding
@@ -120,12 +118,13 @@ class StreamEncrypterImpl implements StreamEncrypter {
 	private void writeStreamHeader() throws IOException {
 		// The header contains the protocol version, stream number and frame key
 		byte[] streamHeaderPlaintext = new byte[STREAM_HEADER_PLAINTEXT_LENGTH];
-		writeUint16(PROTOCOL_VERSION, streamHeaderPlaintext, 0);
-		writeUint64(streamNumber, streamHeaderPlaintext, INT_16_BYTES);
-		arraycopy(frameKey.getBytes(), 0, streamHeaderPlaintext,
+		ByteUtils.writeUint16(PROTOCOL_VERSION, streamHeaderPlaintext, 0);
+		ByteUtils.writeUint64(streamNumber, streamHeaderPlaintext,
+				INT_16_BYTES);
+		System.arraycopy(frameKey.getBytes(), 0, streamHeaderPlaintext,
 				INT_16_BYTES + INT_64_BYTES, SecretKey.LENGTH);
 		byte[] streamHeaderCiphertext = new byte[STREAM_HEADER_LENGTH];
-		arraycopy(streamHeaderNonce, 0, streamHeaderCiphertext, 0,
+		System.arraycopy(streamHeaderNonce, 0, streamHeaderCiphertext, 0,
 				STREAM_HEADER_NONCE_LENGTH);
 		// Encrypt and authenticate the stream header key
 		try {

bramble-core/src/main/java/org/briarproject/bramble/crypto/TransportCryptoImpl.java

@@ -7,12 +7,13 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.transport.IncomingKeys;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.TransportKeys;
+import org.briarproject.bramble.util.ByteUtils;
+import org.briarproject.bramble.util.StringUtils;
 import org.spongycastle.crypto.Digest;
 import org.spongycastle.crypto.digests.Blake2bDigest;
 
 import javax.inject.Inject;
 
-import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_HEADER_LABEL;
 import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_TAG_LABEL;
 import static org.briarproject.bramble.api.transport.TransportConstants.BOB_HEADER_LABEL;
@@ -23,9 +24,6 @@ import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.MAX_16_BIT_UNSIGNED;
 import static org.briarproject.bramble.util.ByteUtils.MAX_32_BIT_UNSIGNED;
-import static org.briarproject.bramble.util.ByteUtils.writeUint16;
-import static org.briarproject.bramble.util.ByteUtils.writeUint64;
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
 
 class TransportCryptoImpl implements TransportCrypto {
 
@@ -93,21 +91,21 @@ class TransportCryptoImpl implements TransportCrypto {
 
 	private SecretKey rotateKey(SecretKey k, long rotationPeriod) {
 		byte[] period = new byte[INT_64_BYTES];
-		writeUint64(rotationPeriod, period, 0);
+		ByteUtils.writeUint64(rotationPeriod, period, 0);
 		return crypto.deriveKey(ROTATE_LABEL, k, period);
 	}
 
 	private SecretKey deriveTagKey(SecretKey master, TransportId t,
 			boolean alice) {
 		String label = alice ? ALICE_TAG_LABEL : BOB_TAG_LABEL;
-		byte[] id = toUtf8(t.getString());
+		byte[] id = StringUtils.toUtf8(t.getString());
 		return crypto.deriveKey(label, master, id);
 	}
 
 	private SecretKey deriveHeaderKey(SecretKey master, TransportId t,
 			boolean alice) {
 		String label = alice ? ALICE_HEADER_LABEL : BOB_HEADER_LABEL;
-		byte[] id = toUtf8(t.getString());
+		byte[] id = StringUtils.toUtf8(t.getString());
 		return crypto.deriveKey(label, master, id);
 	}
 
@@ -127,14 +125,14 @@ class TransportCryptoImpl implements TransportCrypto {
 		// The input is the protocol version as a 16-bit integer, followed by
 		// the stream number as a 64-bit integer
 		byte[] protocolVersionBytes = new byte[INT_16_BYTES];
-		writeUint16(protocolVersion, protocolVersionBytes, 0);
+		ByteUtils.writeUint16(protocolVersion, protocolVersionBytes, 0);
 		prf.update(protocolVersionBytes, 0, protocolVersionBytes.length);
 		byte[] streamNumberBytes = new byte[INT_64_BYTES];
-		writeUint64(streamNumber, streamNumberBytes, 0);
+		ByteUtils.writeUint64(streamNumber, streamNumberBytes, 0);
 		prf.update(streamNumberBytes, 0, streamNumberBytes.length);
 		byte[] mac = new byte[macLength];
 		prf.doFinal(mac, 0);
 		// The output is the first TAG_LENGTH bytes of the MAC
-		arraycopy(mac, 0, tag, 0, TAG_LENGTH);
+		System.arraycopy(mac, 0, tag, 0, TAG_LENGTH);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -242,7 +242,7 @@ interface Database<T> {
 	 * bytes. This is based on the minimum of the space available on the device
 	 * where the database is stored and the database's configured size.
 	 */
-	long getFreeSpace();
+	long getFreeSpace() throws DbException;
 
 	/**
 	 * Returns the group with the given ID.

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -61,6 +61,7 @@ import org.briarproject.bramble.api.transport.TransportKeys;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -71,9 +72,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
-import static java.util.Collections.singletonList;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
@@ -88,7 +87,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 class DatabaseComponentImpl<T> implements DatabaseComponent {
 
 	private static final Logger LOG =
-			getLogger(DatabaseComponentImpl.class.getName());
+			Logger.getLogger(DatabaseComponentImpl.class.getName());
 
 	private final Database<T> db;
 	private final Class<T> txnClass;
@@ -899,7 +898,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (old == INVISIBLE) db.addGroupVisibility(txn, c, g, v == SHARED);
 		else if (v == INVISIBLE) db.removeGroupVisibility(txn, c, g);
 		else db.setGroupVisibility(txn, c, g, v == SHARED);
-		List<ContactId> affected = singletonList(c);
+		List<ContactId> affected = Collections.singletonList(c);
 		transaction.attach(new GroupVisibilityUpdatedEvent(affected));
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/db/H2Database.java

@@ -7,6 +7,7 @@ import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.util.StringUtils;
 
 import java.io.File;
 import java.sql.Connection;
@@ -22,7 +23,6 @@ import javax.inject.Inject;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
-import static org.briarproject.bramble.util.StringUtils.toHexString;
 
 /**
  * Contains all the H2-specific code for the database.
@@ -107,7 +107,7 @@ class H2Database extends JdbcDatabase {
 		Properties props = new Properties();
 		props.setProperty("user", "user");
 		// Separate the file password from the user password with a space
-		String hex = toHexString(key.getBytes());
+		String hex = StringUtils.toHexString(key.getBytes());
 		props.put("password", hex + " password");
 		return DriverManager.getConnection(getUrl(), props);
 	}

bramble-core/src/main/java/org/briarproject/bramble/db/HyperSqlDatabase.java

@@ -7,6 +7,7 @@ import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.util.StringUtils;
 
 import java.io.File;
 import java.sql.Connection;
@@ -21,7 +22,6 @@ import javax.inject.Inject;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
-import static org.briarproject.bramble.util.StringUtils.toHexString;
 
 /**
  * Contains all the HSQLDB-specific code for the database.
@@ -114,7 +114,7 @@ class HyperSqlDatabase extends JdbcDatabase {
 	protected Connection createConnection() throws SQLException {
 		SecretKey key = this.key;
 		if (key == null) throw new IllegalStateException();
-		String hex = toHexString(key.getBytes());
+		String hex = StringUtils.toHexString(key.getBytes());
 		return DriverManager.getConnection(url + ";crypt_key=" + hex);
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -38,7 +38,9 @@ import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedList;
@@ -52,17 +54,11 @@ import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.GuardedBy;
 
-import static java.lang.System.arraycopy;
 import static java.sql.Types.INTEGER;
 import static java.sql.Types.VARCHAR;
-import static java.util.Arrays.asList;
-import static java.util.Collections.emptyMap;
-import static java.util.Collections.emptySet;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
@@ -313,20 +309,19 @@ abstract class JdbcDatabase implements Database<Connection> {
 			"CREATE INDEX IF NOT EXISTS statusesByContactIdTimestamp"
 					+ " ON statuses (contactId, timestamp)";
 
-	private static final Logger LOG = getLogger(JdbcDatabase.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(JdbcDatabase.class.getName());
 
 	// Different database libraries use different names for certain types
 	private final MessageFactory messageFactory;
 	private final Clock clock;
 	private final DatabaseTypes dbTypes;
 
-	@GuardedBy("connectionsLock")
+	// Locking: connectionsLock
 	private final LinkedList<Connection> connections = new LinkedList<>();
 
-	@GuardedBy("connectionsLock")
-	private int openConnections = 0;
-	@GuardedBy("connectionsLock")
-	private boolean closed = false;
+	private int openConnections = 0; // Locking: connectionsLock
+	private boolean closed = false; // Locking: connectionsLock
 
 	protected abstract Connection createConnection() throws SQLException;
 
@@ -342,7 +337,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		this.clock = clock;
 	}
 
-	@SuppressWarnings("unused")
 	protected void open(String driverClass, boolean reopen, SecretKey key,
 			@Nullable MigrationListener listener) throws DbException {
 		// Load the JDBC driver
@@ -430,7 +424,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
 	List<Migration<Connection>> getMigrations() {
-		return asList(
+		return Arrays.asList(
 				new Migration38_39(),
 				new Migration39_40(),
 				new Migration40_41(dbTypes)
@@ -772,7 +766,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			for (Entry<ContactId, Boolean> e : visibility.entrySet()) {
 				ContactId c = e.getKey();
 				boolean offered = removeOfferedMessage(txn, c, m.getId());
-				boolean seen = offered || c.equals(sender);
+				boolean seen = offered || (sender != null && c.equals(sender));
 				addStatus(txn, m.getId(), c, m.getGroupId(), m.getTimestamp(),
 						raw.length, state, e.getValue(), messageShared,
 						false, seen);
@@ -1542,7 +1536,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (raw == null) throw new MessageDeletedException();
 			if (raw.length <= MESSAGE_HEADER_LENGTH) throw new AssertionError();
 			byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
-			arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
+			System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
 			return new Message(m, g, timestamp, body);
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
@@ -1602,7 +1596,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 				if (intersection == null) intersection = ids;
 				else intersection.retainAll(ids);
 				// Return early if there are no matches
-				if (intersection.isEmpty()) return emptySet();
+				if (intersection.isEmpty()) return Collections.emptySet();
 			}
 			if (intersection == null) throw new AssertionError();
 			return intersection;
@@ -1651,7 +1645,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			GroupId g, Metadata query) throws DbException {
 		// Retrieve the matching message IDs
 		Collection<MessageId> matches = getMessageIds(txn, g, query);
-		if (matches.isEmpty()) return emptyMap();
+		if (matches.isEmpty()) return Collections.emptyMap();
 		// Retrieve the metadata for each match
 		Map<MessageId, Metadata> all = new HashMap<>(matches.size());
 		for (MessageId m : matches) all.put(m, getMessageMetadata(txn, m));
@@ -2401,7 +2395,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 				}
 				ps.close();
 			}
-			if (notRemoved.isEmpty()) return emptyMap();
+			if (notRemoved.isEmpty()) return Collections.emptyMap();
 			// Update any keys that already exist
 			String sql = "UPDATE " + tableName + " SET value = ?"
 					+ " WHERE " + columnName + " = ? AND metaKey = ?";

bramble-core/src/main/java/org/briarproject/bramble/db/Migration38_39.java

@@ -8,12 +8,12 @@ import java.sql.Statement;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
 
 class Migration38_39 implements Migration<Connection> {
 
-	private static final Logger LOG = getLogger(Migration38_39.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(Migration38_39.class.getName());
 
 	@Override
 	public int getStartVersion() {

bramble-core/src/main/java/org/briarproject/bramble/db/Migration39_40.java

@@ -8,12 +8,12 @@ import java.sql.Statement;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
 
 class Migration39_40 implements Migration<Connection> {
 
-	private static final Logger LOG = getLogger(Migration39_40.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(Migration39_40.class.getName());
 
 	@Override
 	public int getStartVersion() {

bramble-core/src/main/java/org/briarproject/bramble/db/Migration40_41.java

@@ -17,7 +17,7 @@ class Migration40_41 implements Migration<Connection> {
 
 	private final DatabaseTypes dbTypes;
 
-	Migration40_41(DatabaseTypes databaseTypes) {
+	public Migration40_41(DatabaseTypes databaseTypes) {
 		this.dbTypes = databaseTypes;
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/identity/AuthorFactoryImpl.java

@@ -7,6 +7,8 @@ import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.util.ByteUtils;
+import org.briarproject.bramble.util.StringUtils;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
@@ -14,8 +16,6 @@ import javax.inject.Inject;
 import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
 import static org.briarproject.bramble.api.identity.AuthorId.LABEL;
 import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.writeUint32;
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
 
 @Immutable
 @NotNullByDefault
@@ -58,8 +58,8 @@ class AuthorFactoryImpl implements AuthorFactory {
 
 	private AuthorId getId(int formatVersion, String name, byte[] publicKey) {
 		byte[] formatVersionBytes = new byte[INT_32_BYTES];
-		writeUint32(formatVersion, formatVersionBytes, 0);
+		ByteUtils.writeUint32(formatVersion, formatVersionBytes, 0);
 		return new AuthorId(crypto.hash(LABEL, formatVersionBytes,
-				toUtf8(name), publicKey));
+				StringUtils.toUtf8(name), publicKey));
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/identity/IdentityManagerImpl.java

@@ -16,7 +16,6 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
 
@@ -25,7 +24,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 class IdentityManagerImpl implements IdentityManager {
 
 	private static final Logger LOG =
-			getLogger(IdentityManagerImpl.class.getName());
+			Logger.getLogger(IdentityManagerImpl.class.getName());
 
 	private final DatabaseComponent db;
 	private final CryptoComponent crypto;

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/AbortException.java

@@ -2,7 +2,7 @@ package org.briarproject.bramble.keyagreement;
 
 class AbortException extends Exception {
 
-	final boolean receivedAbort;
+	boolean receivedAbort;
 
 	AbortException() {
 		this(false);

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/ConnectionChooserImpl.java

@@ -20,14 +20,13 @@ import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
 
 @NotNullByDefault
 @ThreadSafe
 class ConnectionChooserImpl implements ConnectionChooser {
 
 	private static final Logger LOG =
-			getLogger(ConnectionChooserImpl.class.getName());
+			Logger.getLogger(ConnectionChooserImpl.class.getName());
 
 	private final Clock clock;
 	private final Executor ioExecutor;

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementConnector.java

@@ -30,7 +30,6 @@ import javax.annotation.Nullable;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.CONNECTION_TIMEOUT;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
@@ -42,7 +41,7 @@ class KeyAgreementConnector {
 	}
 
 	private static final Logger LOG =
-			getLogger(KeyAgreementConnector.class.getName());
+			Logger.getLogger(KeyAgreementConnector.class.getName());
 
 	private final Callbacks callbacks;
 	private final KeyAgreementCrypto keyAgreementCrypto;

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementTaskImpl.java

@@ -28,7 +28,6 @@ import java.util.logging.Logger;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @MethodsNotNullByDefault
@@ -37,7 +36,7 @@ class KeyAgreementTaskImpl extends Thread implements KeyAgreementTask,
 		KeyAgreementProtocol.Callbacks, KeyAgreementConnector.Callbacks {
 
 	private static final Logger LOG =
-			getLogger(KeyAgreementTaskImpl.class.getName());
+			Logger.getLogger(KeyAgreementTaskImpl.class.getName());
 
 	private final CryptoComponent crypto;
 	private final KeyAgreementCrypto keyAgreementCrypto;

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementTransport.java

@@ -16,7 +16,6 @@ import java.io.OutputStream;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.PROTOCOL_VERSION;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.ABORT;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.CONFIRM;
@@ -30,7 +29,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 class KeyAgreementTransport {
 
 	private static final Logger LOG =
-			getLogger(KeyAgreementTransport.class.getName());
+			Logger.getLogger(KeyAgreementTransport.class.getName());
 
 	private final KeyAgreementConnection kac;
 	private final RecordReader reader;

bramble-core/src/main/java/org/briarproject/bramble/lifecycle/LifecycleManagerImpl.java

@@ -28,7 +28,6 @@ import javax.inject.Inject;
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.COMPACTING_DATABASE;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.MIGRATING_DATABASE;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.RUNNING;
@@ -50,7 +49,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 
 	private static final Logger LOG =
-			getLogger(LifecycleManagerImpl.class.getName());
+			Logger.getLogger(LifecycleManagerImpl.class.getName());
 
 	private final DatabaseComponent db;
 	private final EventBus eventBus;

bramble-core/src/main/java/org/briarproject/bramble/plugin/ConnectionManagerImpl.java

@@ -26,14 +26,13 @@ import java.util.logging.Logger;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 class ConnectionManagerImpl implements ConnectionManager {
 
 	private static final Logger LOG =
-			getLogger(ConnectionManagerImpl.class.getName());
+			Logger.getLogger(ConnectionManagerImpl.class.getName());
 
 	private final Executor ioExecutor;
 	private final KeyManager keyManager;

bramble-core/src/main/java/org/briarproject/bramble/plugin/ConnectionRegistryImpl.java

@@ -13,6 +13,7 @@ import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -23,16 +24,14 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
-import static java.util.Collections.emptyList;
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
 
 @ThreadSafe
 @NotNullByDefault
 class ConnectionRegistryImpl implements ConnectionRegistry {
 
 	private static final Logger LOG =
-			getLogger(ConnectionRegistryImpl.class.getName());
+			Logger.getLogger(ConnectionRegistryImpl.class.getName());
 
 	private final EventBus eventBus;
 	private final Lock lock = new ReentrantLock();
@@ -104,7 +103,7 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 		lock.lock();
 		try {
 			Multiset<ContactId> m = connections.get(t);
-			if (m == null) return emptyList();
+			if (m == null) return Collections.emptyList();
 			List<ContactId> ids = new ArrayList<>(m.keySet());
 			if (LOG.isLoggable(INFO))
 				LOG.info(ids.size() + " contacts connected: " + t);

bramble-core/src/main/java/org/briarproject/bramble/plugin/PluginManagerImpl.java

@@ -52,7 +52,6 @@ import javax.inject.Inject;
 import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
@@ -62,7 +61,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 class PluginManagerImpl implements PluginManager, Service {
 
 	private static final Logger LOG =
-			getLogger(PluginManagerImpl.class.getName());
+			Logger.getLogger(PluginManagerImpl.class.getName());
 
 	private final Executor ioExecutor;
 	private final ScheduledExecutorService scheduler;

bramble-core/src/main/java/org/briarproject/bramble/plugin/Poller.java

@@ -36,20 +36,18 @@ import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Logger;
 
-import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @ThreadSafe
 @NotNullByDefault
 class Poller implements EventListener {
 
-	private static final Logger LOG = getLogger(Poller.class.getName());
+	private static final Logger LOG = Logger.getLogger(Poller.class.getName());
 
 	private final Executor ioExecutor;
 	private final ScheduledExecutorService scheduler;
@@ -60,8 +58,7 @@ class Poller implements EventListener {
 	private final SecureRandom random;
 	private final Clock clock;
 	private final Lock lock;
-	@GuardedBy("lock")
-	private final Map<TransportId, ScheduledPollTask> tasks;
+	private final Map<TransportId, ScheduledPollTask> tasks; // Locking: lock
 
 	Poller(@IoExecutor Executor ioExecutor,
 			@Scheduler ScheduledExecutorService scheduler,

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothConnectionLimiter.java

@@ -20,7 +20,6 @@ interface BluetoothConnectionLimiter {
 	 * Returns true if a contact connection can be opened. This method does not
 	 * need to be called for key agreement connections.
 	 */
-	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	boolean canOpenContactConnection();
 
 	/**

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothConnectionLimiterImpl.java

@@ -13,7 +13,6 @@ import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
@@ -21,7 +20,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 class BluetoothConnectionLimiterImpl implements BluetoothConnectionLimiter {
 
 	private static final Logger LOG =
-			getLogger(BluetoothConnectionLimiterImpl.class.getName());
+			Logger.getLogger(BluetoothConnectionLimiterImpl.class.getName());
 
 	private final Object lock = new Object();
 	// The following are locking: lock

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothPlugin.java

@@ -37,7 +37,6 @@ import javax.annotation.Nullable;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_BLUETOOTH;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_BT_ENABLE;
@@ -55,7 +54,7 @@ import static org.briarproject.bramble.util.StringUtils.macToString;
 abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 
 	private static final Logger LOG =
-			getLogger(BluetoothPlugin.class.getName());
+			Logger.getLogger(BluetoothPlugin.class.getName());
 
 	final BluetoothConnectionLimiter connectionLimiter;
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/FilePlugin.java

@@ -14,7 +14,6 @@ import java.io.IOException;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.plugin.FileConstants.PROP_PATH;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
@@ -22,7 +21,8 @@ import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 @NotNullByDefault
 abstract class FilePlugin implements SimplexPlugin {
 
-	private static final Logger LOG = getLogger(FilePlugin.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(FilePlugin.class.getName());
 
 	protected final SimplexPluginCallback callback;
 	protected final int maxLatency;

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/FileTransportReader.java

@@ -8,14 +8,13 @@ import java.io.InputStream;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
 
 @NotNullByDefault
 class FileTransportReader implements TransportConnectionReader {
 
 	private static final Logger LOG =
-			getLogger(FileTransportReader.class.getName());
+			Logger.getLogger(FileTransportReader.class.getName());
 
 	private final File file;
 	private final InputStream in;

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/FileTransportWriter.java

@@ -8,14 +8,13 @@ import java.io.OutputStream;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
 
 @NotNullByDefault
 class FileTransportWriter implements TransportConnectionWriter {
 
 	private static final Logger LOG =
-			getLogger(FileTransportWriter.class.getName());
+			Logger.getLogger(FileTransportWriter.class.getName());
 
 	private final File file;
 	private final OutputStream out;

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/LanTcpPlugin.java

@@ -12,6 +12,7 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.util.IoUtils;
+import org.briarproject.bramble.util.StringUtils;
 
 import java.io.IOException;
 import java.net.Inet4Address;
@@ -22,30 +23,26 @@ import java.net.Socket;
 import java.net.SocketAddress;
 import java.net.UnknownHostException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
-import static java.util.Collections.addAll;
-import static java.util.Collections.emptyList;
-import static java.util.Collections.sort;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_LAN;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.ID;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.PREF_LAN_IP_PORTS;
 import static org.briarproject.bramble.api.plugin.LanTcpConstants.PROP_IP_PORTS;
 import static org.briarproject.bramble.util.ByteUtils.MAX_16_BIT_UNSIGNED;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubSocketAddress;
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-import static org.briarproject.bramble.util.StringUtils.join;
 
 @NotNullByDefault
 class LanTcpPlugin extends TcpPlugin {
 
-	private static final Logger LOG = getLogger(LanTcpPlugin.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(LanTcpPlugin.class.getName());
 
 	private static final LanAddressComparator ADDRESS_COMPARATOR =
 			new LanAddressComparator();
@@ -80,13 +77,12 @@ class LanTcpPlugin extends TcpPlugin {
 				locals.add(new InetSocketAddress(local, 0));
 			}
 		}
-		//noinspection Java8ListSort
-		sort(locals, ADDRESS_COMPARATOR);
+		Collections.sort(locals, ADDRESS_COMPARATOR);
 		return locals;
 	}
 
 	private List<InetSocketAddress> parseSocketAddresses(String ipPorts) {
-		if (isNullOrEmpty(ipPorts)) return emptyList();
+		if (StringUtils.isNullOrEmpty(ipPorts)) return Collections.emptyList();
 		String[] split = ipPorts.split(SEPARATOR);
 		List<InetSocketAddress> addresses = new ArrayList<>();
 		for (String ipPort : split) {
@@ -102,23 +98,24 @@ class LanTcpPlugin extends TcpPlugin {
 		// Get the list of recently used addresses
 		String setting = callback.getSettings().get(PREF_LAN_IP_PORTS);
 		List<String> recent = new ArrayList<>();
-		if (!isNullOrEmpty(setting)) addAll(recent, setting.split(SEPARATOR));
+		if (!StringUtils.isNullOrEmpty(setting))
+			Collections.addAll(recent, setting.split(SEPARATOR));
 		// Is the address already in the list?
 		if (recent.remove(ipPort)) {
 			// Move the address to the start of the list
 			recent.add(0, ipPort);
-			setting = join(recent, SEPARATOR);
+			setting = StringUtils.join(recent, SEPARATOR);
 		} else {
 			// Add the address to the start of the list
 			recent.add(0, ipPort);
 			// Drop the least recently used address if the list is full
 			if (recent.size() > MAX_ADDRESSES)
 				recent = recent.subList(0, MAX_ADDRESSES);
-			setting = join(recent, SEPARATOR);
+			setting = StringUtils.join(recent, SEPARATOR);
 			// Update the list of addresses shared with contacts
 			List<String> shared = new ArrayList<>(recent);
-			sort(shared);
-			String property = join(shared, SEPARATOR);
+			Collections.sort(shared);
+			String property = StringUtils.join(shared, SEPARATOR);
 			TransportProperties properties = new TransportProperties();
 			properties.put(PROP_IP_PORTS, property);
 			callback.mergeLocalProperties(properties);

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/PortMapperImpl.java

@@ -17,7 +17,6 @@ import javax.xml.parsers.ParserConfigurationException;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubInetAddress;
 
@@ -26,7 +25,8 @@ import static org.briarproject.bramble.util.PrivacyUtils.scrubInetAddress;
 @ParametersNotNullByDefault
 class PortMapperImpl implements PortMapper {
 
-	private static final Logger LOG = getLogger(PortMapperImpl.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(PortMapperImpl.class.getName());
 
 	private final ShutdownManager shutdownManager;
 	private final AtomicBoolean started = new AtomicBoolean(false);

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/TcpPlugin.java

@@ -12,6 +12,7 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.util.IoUtils;
+import org.briarproject.bramble.util.StringUtils;
 
 import java.io.IOException;
 import java.net.InetAddress;
@@ -40,19 +41,17 @@ import static java.util.Collections.emptyList;
 import static java.util.Collections.list;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubSocketAddress;
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 abstract class TcpPlugin implements DuplexPlugin {
 
-	private static final Logger LOG = getLogger(TcpPlugin.class.getName());
-
 	private static final Pattern DOTTED_QUAD =
 			Pattern.compile("^\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}$");
+	private static final Logger LOG =
+			Logger.getLogger(TcpPlugin.class.getName());
 
 	protected final Executor ioExecutor, bindExecutor;
 	protected final Backoff backoff;
@@ -85,7 +84,6 @@ abstract class TcpPlugin implements DuplexPlugin {
 	/**
 	 * Returns true if connections to the given address can be attempted.
 	 */
-	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	protected abstract boolean isConnectable(InetSocketAddress remote);
 
 	TcpPlugin(Executor ioExecutor, Backoff backoff,
@@ -265,7 +263,7 @@ abstract class TcpPlugin implements DuplexPlugin {
 
 	@Nullable
 	InetSocketAddress parseSocketAddress(String ipPort) {
-		if (isNullOrEmpty(ipPort)) return null;
+		if (StringUtils.isNullOrEmpty(ipPort)) return null;
 		String[] split = ipPort.split(":");
 		if (split.length != 2) return null;
 		String addr = split[0], port = split[1];

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/WanTcpPlugin.java

@@ -10,12 +10,11 @@ import org.briarproject.bramble.api.properties.TransportProperties;
 import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
+import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.Executor;
 
-import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.plugin.WanTcpConstants.ID;
 
 @MethodsNotNullByDefault
@@ -81,7 +80,8 @@ class WanTcpPlugin extends TcpPlugin {
 	protected List<InetSocketAddress> getRemoteSocketAddresses(
 			TransportProperties p) {
 		InetSocketAddress parsed = parseSocketAddress(p.get(PROP_IP_PORT));
-		return parsed == null ? emptyList() : singletonList(parsed);
+		if (parsed == null) return Collections.emptyList();
+		return Collections.singletonList(parsed);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/TorPlugin.java

@@ -42,7 +42,9 @@ import java.net.InetSocketAddress;
 import java.net.ServerSocket;
 import java.net.Socket;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -56,12 +58,8 @@ import java.util.zip.ZipInputStream;
 import javax.annotation.Nullable;
 import javax.net.SocketFactory;
 
-import static java.util.Arrays.asList;
-import static java.util.Collections.singletonList;
-import static java.util.Collections.singletonMap;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static net.freehaven.tor.control.TorControlCommands.HS_ADDRESS;
 import static net.freehaven.tor.control.TorControlCommands.HS_PRIVKEY;
 import static org.briarproject.bramble.api.plugin.TorConstants.CONTROL_PORT;
@@ -71,11 +69,9 @@ import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_AUTOMATIC;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_NEVER;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_WITH_BRIDGES;
-import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_ONLY_WHEN_CHARGING;
 import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_PORT;
 import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V2;
 import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION_V3;
-import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubOnion;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
@@ -84,7 +80,8 @@ import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 @ParametersNotNullByDefault
 abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
-	private static final Logger LOG = getLogger(TorPlugin.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(TorPlugin.class.getName());
 
 	private static final String[] EVENTS = {
 			"CIRC", "ORCONN", "HS_DESC", "NOTICE", "WARN", "ERR"
@@ -253,11 +250,11 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			controlConnection.authenticate(read(cookieFile));
 			// Tell Tor to exit when the control connection is closed
 			controlConnection.takeOwnership();
-			controlConnection.resetConf(singletonList(OWNER));
+			controlConnection.resetConf(Collections.singletonList(OWNER));
 			running = true;
 			// Register to receive events from the Tor process
 			controlConnection.setEventHandler(this);
-			controlConnection.setEvents(asList(EVENTS));
+			controlConnection.setEvents(Arrays.asList(EVENTS));
 			// Check whether Tor has already bootstrapped
 			String phase = controlConnection.getInfo("status/bootstrap-phase");
 			if (phase != null && phase.contains("PROGRESS=100")) {
@@ -282,31 +279,28 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		InputStream in = null;
 		OutputStream out = null;
 		try {
-			// The done file may already exist from a previous installation
-			//noinspection ResultOfMethodCallIgnored
 			doneFile.delete();
 			// Unzip the Tor binary to the filesystem
 			in = getTorInputStream();
 			out = new FileOutputStream(torFile);
-			copyAndClose(in, out);
+			IoUtils.copyAndClose(in, out);
 			// Make the Tor binary executable
 			if (!torFile.setExecutable(true, true)) throw new IOException();
 			// Unzip the GeoIP database to the filesystem
 			in = getGeoIpInputStream();
 			out = new FileOutputStream(geoIpFile);
-			copyAndClose(in, out);
+			IoUtils.copyAndClose(in, out);
 			// Unzip the Obfs4 proxy to the filesystem
 			in = getObfs4InputStream();
 			out = new FileOutputStream(obfs4File);
-			copyAndClose(in, out);
+			IoUtils.copyAndClose(in, out);
 			// Make the Obfs4 proxy executable
 			if (!obfs4File.setExecutable(true, true)) throw new IOException();
 			// Copy the config file to the filesystem
 			in = getConfigInputStream();
 			out = new FileOutputStream(configFile);
-			copyAndClose(in, out);
-			if (!doneFile.createNewFile())
-				LOG.warning("Failed to create done file");
+			IoUtils.copyAndClose(in, out);
+			doneFile.createNewFile();
 		} catch (IOException e) {
 			IoUtils.tryToClose(in, LOG, WARNING);
 			IoUtils.tryToClose(out, LOG, WARNING);
@@ -415,7 +409,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (!running) return;
 		LOG.info("Creating hidden service");
 		String privKey = settings.get(HS_PRIVKEY);
-		Map<Integer, String> portLines = singletonMap(80, "127.0.0.1:" + port);
+		Map<Integer, String> portLines =
+				Collections.singletonMap(80, "127.0.0.1:" + port);
 		Map<String, String> response;
 		try {
 			// Use the control connection to set up the hidden service
@@ -653,10 +648,8 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			if (s.getNamespace().equals(ID.getString())) {
 				LOG.info("Tor settings updated");
 				settings = s.getSettings();
-				// Works around a bug introduced in Tor 0.3.4.8.
-				// https://trac.torproject.org/projects/tor/ticket/28027
-				// Could be replaced with callback.transportDisabled()
-				// when fixed.
+				// Works around a bug introduced in Tor 0.3.4.8. Could be
+				// replaced with callback.transportDisabled() when fixed.
 				disableNetwork();
 				updateConnectionStatus(networkManager.getNetworkStatus(),
 						batteryManager.isCharging());
@@ -692,8 +685,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			int network = settings.getInt(PREF_TOR_NETWORK,
 					PREF_TOR_NETWORK_AUTOMATIC);
 			boolean useMobile = settings.getBoolean(PREF_TOR_MOBILE, true);
-			boolean onlyWhenCharging =
-					settings.getBoolean(PREF_TOR_ONLY_WHEN_CHARGING, false);
 			boolean bridgesWork = circumventionProvider.doBridgesWork(country);
 			boolean automatic = network == PREF_TOR_NETWORK_AUTOMATIC;
 
@@ -708,12 +699,9 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				if (!online) {
 					LOG.info("Disabling network, device is offline");
 					enableNetwork(false);
-				} else if (!charging && onlyWhenCharging) {
-					LOG.info("Disabling network, device is on battery");
-					enableNetwork(false);
 				} else if (network == PREF_TOR_NETWORK_NEVER ||
 						(!useMobile && !wifi)) {
-					LOG.info("Disabling network, device is using mobile data");
+					LOG.info("Disabling network due to setting");
 					enableNetwork(false);
 				} else if (automatic && blocked && !bridgesWork) {
 					LOG.info("Disabling network, country is blocked");

bramble-core/src/main/java/org/briarproject/bramble/record/RecordReaderImpl.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.record.Record;
 import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.util.ByteUtils;
 
 import java.io.DataInputStream;
 import java.io.IOException;
@@ -13,7 +14,6 @@ import javax.annotation.concurrent.NotThreadSafe;
 
 import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
 import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.readUint16;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -31,7 +31,7 @@ class RecordReaderImpl implements RecordReader {
 		in.readFully(header);
 		byte protocolVersion = header[0];
 		byte recordType = header[1];
-		int payloadLength = readUint16(header, 2);
+		int payloadLength = ByteUtils.readUint16(header, 2);
 		if (payloadLength < 0 || payloadLength > MAX_RECORD_PAYLOAD_BYTES)
 			throw new FormatException();
 		byte[] payload = new byte[payloadLength];

bramble-core/src/main/java/org/briarproject/bramble/record/RecordWriterImpl.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.record;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.record.Record;
 import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.util.ByteUtils;
 
 import java.io.IOException;
 import java.io.OutputStream;
@@ -10,7 +11,6 @@ import java.io.OutputStream;
 import javax.annotation.concurrent.NotThreadSafe;
 
 import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.writeUint16;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -28,7 +28,7 @@ class RecordWriterImpl implements RecordWriter {
 		byte[] payload = r.getPayload();
 		header[0] = r.getProtocolVersion();
 		header[1] = r.getRecordType();
-		writeUint16(payload.length, header, 2);
+		ByteUtils.writeUint16(payload.length, header, 2);
 		out.write(header);
 		out.write(payload);
 	}

bramble-core/src/main/java/org/briarproject/bramble/reliability/Ack.java

@@ -1,12 +1,10 @@
 package org.briarproject.bramble.reliability;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.ByteUtils;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static org.briarproject.bramble.util.ByteUtils.readUint16;
-import static org.briarproject.bramble.util.ByteUtils.writeUint16;
-
 @NotThreadSafe
 @NotNullByDefault
 class Ack extends Frame {
@@ -25,10 +23,10 @@ class Ack extends Frame {
 	}
 
 	int getWindowSize() {
-		return readUint16(buf, 5);
+		return ByteUtils.readUint16(buf, 5);
 	}
 
 	void setWindowSize(int windowSize) {
-		writeUint16(windowSize, buf, 5);
+		ByteUtils.writeUint16(windowSize, buf, 5);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/reliability/Frame.java

@@ -1,19 +1,17 @@
 package org.briarproject.bramble.reliability;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.ByteUtils;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static org.briarproject.bramble.util.ByteUtils.readUint32;
-import static org.briarproject.bramble.util.ByteUtils.writeUint32;
-
 @NotThreadSafe
 @NotNullByDefault
 abstract class Frame {
 
 	static final byte ACK_FLAG = (byte) 128, FIN_FLAG = 64;
 
-	final byte[] buf;
+	protected final byte[] buf;
 
 	Frame(byte[] buf) {
 		this.buf = buf;
@@ -28,11 +26,11 @@ abstract class Frame {
 	}
 
 	long getChecksum() {
-		return readUint32(buf, buf.length - 4);
+		return ByteUtils.readUint32(buf, buf.length - 4);
 	}
 
 	void setChecksum(long checksum) {
-		writeUint32(checksum, buf, buf.length - 4);
+		ByteUtils.writeUint32(checksum, buf, buf.length - 4);
 	}
 
 	long calculateChecksum() {
@@ -40,11 +38,11 @@ abstract class Frame {
 	}
 
 	long getSequenceNumber() {
-		return readUint32(buf, 1);
+		return ByteUtils.readUint32(buf, 1);
 	}
 
 	void setSequenceNumber(long sequenceNumber) {
-		writeUint32(sequenceNumber, buf, 1);
+		ByteUtils.writeUint32(sequenceNumber, buf, 1);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/reliability/Receiver.java

@@ -101,7 +101,6 @@ class Receiver implements ReadHandler {
 		}
 	}
 
-	@SuppressWarnings("StatementWithEmptyBody")
 	private void handleData(byte[] b) throws IOException {
 		windowLock.lock();
 		try {
@@ -125,7 +124,6 @@ class Receiver implements ReadHandler {
 				finalSequenceNumber = sequenceNumber;
 				// Remove any data frames with higher sequence numbers
 				Iterator<Data> it = dataFrames.iterator();
-				//noinspection Java8CollectionRemoveIf
 				while (it.hasNext()) {
 					Data d1 = it.next();
 					if (d1.getSequenceNumber() >= finalSequenceNumber)
@@ -150,7 +148,6 @@ class Receiver implements ReadHandler {
 
 	private static class SequenceNumberComparator implements Comparator<Data> {
 
-		@SuppressWarnings("UseCompareMethod")
 		@Override
 		public int compare(Data d1, Data d2) {
 			long s1 = d1.getSequenceNumber(), s2 = d2.getSequenceNumber();

bramble-core/src/main/java/org/briarproject/bramble/reliability/ReceiverInputStream.java

@@ -8,8 +8,6 @@ import java.io.InputStream;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.lang.System.arraycopy;
-
 @NotThreadSafe
 @NotNullByDefault
 class ReceiverInputStream extends InputStream {
@@ -46,13 +44,12 @@ class ReceiverInputStream extends InputStream {
 		while (length == 0) if (!receive()) return -1;
 		if (data == null) throw new AssertionError();
 		len = Math.min(len, length);
-		arraycopy(data.getBuffer(), offset, b, off, len);
+		System.arraycopy(data.getBuffer(), offset, b, off, len);
 		offset += len;
 		length -= len;
 		return len;
 	}
 
-	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	private boolean receive() throws IOException {
 		if (length != 0) throw new AssertionError();
 		if (data != null && data.isLastFrame()) {

bramble-core/src/main/java/org/briarproject/bramble/reliability/ReliabilityLayerImpl.java

@@ -16,7 +16,6 @@ import java.util.logging.Logger;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @MethodsNotNullByDefault
@@ -26,7 +25,7 @@ class ReliabilityLayerImpl implements ReliabilityLayer, WriteHandler {
 	private static final int TICK_INTERVAL = 500; // Milliseconds
 
 	private static final Logger LOG =
-			getLogger(ReliabilityLayerImpl.class.getName());
+			Logger.getLogger(ReliabilityLayerImpl.class.getName());
 
 	private final Executor executor;
 	private final Clock clock;

bramble-core/src/main/java/org/briarproject/bramble/reliability/Sender.java

@@ -16,7 +16,6 @@ import java.util.concurrent.locks.ReentrantLock;
 import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 
 @ThreadSafe
 @NotNullByDefault
@@ -97,7 +96,7 @@ class Sender {
 			}
 			// If any older data frames are outstanding, retransmit the oldest
 			if (foundIndex > 0) {
-				fastRetransmit = requireNonNull(outstanding.poll());
+				fastRetransmit = outstanding.poll();
 				fastRetransmit.lastTransmitted = now;
 				fastRetransmit.retransmitted = true;
 				outstanding.add(fastRetransmit);
@@ -192,7 +191,7 @@ class Sender {
 		writeHandler.handleWrite(d.getBuffer());
 	}
 
-	void flush() throws InterruptedException {
+	void flush() throws IOException, InterruptedException {
 		windowLock.lock();
 		try {
 			while (dataWaiting || !outstanding.isEmpty())

bramble-core/src/main/java/org/briarproject/bramble/reliability/SenderOutputStream.java

@@ -7,8 +7,6 @@ import java.io.OutputStream;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.lang.System.arraycopy;
-
 @NotThreadSafe
 @NotNullByDefault
 class SenderOutputStream extends OutputStream {
@@ -61,20 +59,20 @@ class SenderOutputStream extends OutputStream {
 	public void write(byte[] b, int off, int len) throws IOException {
 		int available = Data.MAX_LENGTH - offset - Data.FOOTER_LENGTH;
 		while (available <= len) {
-			arraycopy(b, off, buf, offset, available);
+			System.arraycopy(b, off, buf, offset, available);
 			offset += available;
 			send(false);
 			off += available;
 			len -= available;
 			available = Data.MAX_LENGTH - offset - Data.FOOTER_LENGTH;
 		}
-		arraycopy(b, off, buf, offset, len);
+		System.arraycopy(b, off, buf, offset, len);
 		offset += len;
 	}
 
 	private void send(boolean lastFrame) throws IOException {
 		byte[] frame = new byte[offset + Data.FOOTER_LENGTH];
-		arraycopy(buf, 0, frame, 0, frame.length);
+		System.arraycopy(buf, 0, frame, 0, frame.length);
 		Data d = new Data(frame);
 		d.setLastFrame(lastFrame);
 		d.setSequenceNumber(sequenceNumber++);

bramble-core/src/main/java/org/briarproject/bramble/reliability/SlipDecoder.java

@@ -7,8 +7,6 @@ import java.io.IOException;
 
 import javax.annotation.concurrent.Immutable;
 
-import static java.lang.System.arraycopy;
-
 @Immutable
 @NotNullByDefault
 class SlipDecoder implements ReadHandler {
@@ -38,7 +36,7 @@ class SlipDecoder implements ReadHandler {
 				} else {
 					if (decodedLength > 0) {
 						byte[] decoded = new byte[decodedLength];
-						arraycopy(buf, 0, decoded, 0, decodedLength);
+						System.arraycopy(buf, 0, decoded, 0, decodedLength);
 						readHandler.handleRead(decoded);
 					}
 					reset(false);

bramble-core/src/main/java/org/briarproject/bramble/reporting/DevReportServer.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.reporting;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.IoUtils;
 
 import java.io.Closeable;
 import java.io.File;
@@ -16,9 +17,6 @@ import java.util.concurrent.Semaphore;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
-import static java.io.File.createTempFile;
-import static org.briarproject.bramble.util.IoUtils.getInputStream;
-
 @Immutable
 @NotNullByDefault
 public class DevReportServer {
@@ -44,7 +42,6 @@ public class DevReportServer {
 		TokenBucket bucket = new TokenBucket();
 		bucket.start();
 		try {
-			//noinspection InfiniteLoopStatement
 			while (true) {
 				Socket s = ss.accept();
 				System.out.println("Incoming connection");
@@ -104,7 +101,6 @@ public class DevReportServer {
 		@Override
 		public void run() {
 			try {
-				//noinspection InfiniteLoopStatement
 				while (true) {
 					// If the bucket isn't full, add a token
 					if (semaphore.availablePermits() < MAX_TOKENS) {
@@ -135,11 +131,9 @@ public class DevReportServer {
 			OutputStream out = null;
 			try {
 				socket.setSoTimeout(SOCKET_TIMEOUT_MS);
-				in = getInputStream(socket);
-				// Directory may already exist
-				//noinspection ResultOfMethodCallIgnored
+				in = IoUtils.getInputStream(socket);
 				reportDir.mkdirs();
-				reportFile = createTempFile(FILE_PREFIX, FILE_SUFFIX,
+				reportFile = File.createTempFile(FILE_PREFIX, FILE_SUFFIX,
 						reportDir);
 				out = new FileOutputStream(reportFile);
 				System.out.println("Saving report to " + reportFile);
@@ -157,8 +151,7 @@ public class DevReportServer {
 				System.out.println("Saved " + length + " bytes");
 			} catch (IOException e) {
 				e.printStackTrace();
-				if (reportFile != null && !reportFile.delete())
-					System.err.println("Failed to delete report");
+				if (reportFile != null) reportFile.delete();
 			} finally {
 				tryToClose(in);
 				tryToClose(out);

bramble-core/src/main/java/org/briarproject/bramble/reporting/DevReporterImpl.java

@@ -9,6 +9,8 @@ import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.plugin.event.TransportEnabledEvent;
 import org.briarproject.bramble.api.reporting.DevConfig;
 import org.briarproject.bramble.api.reporting.DevReporter;
+import org.briarproject.bramble.util.IoUtils;
+import org.briarproject.bramble.util.StringUtils;
 
 import java.io.File;
 import java.io.FileInputStream;
@@ -28,18 +30,14 @@ import javax.inject.Inject;
 import javax.net.SocketFactory;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.IoUtils.copyAndClose;
-import static org.briarproject.bramble.util.IoUtils.getOutputStream;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
 
 @Immutable
 @NotNullByDefault
 class DevReporterImpl implements DevReporter, EventListener {
 
 	private static final Logger LOG =
-			getLogger(DevReporterImpl.class.getName());
+			Logger.getLogger(DevReporterImpl.class.getName());
 
 	private static final int SOCKET_TIMEOUT = 30 * 1000; // 30 seconds
 	private static final int LINE_LENGTH = 70;
@@ -75,7 +73,7 @@ class DevReporterImpl implements DevReporter, EventListener {
 	public void encryptReportToFile(File reportDir, String filename,
 			String report) throws FileNotFoundException {
 		LOG.info("Encrypting report to file");
-		byte[] plaintext = toUtf8(report);
+		byte[] plaintext = StringUtils.toUtf8(report);
 		byte[] ciphertext = crypto.encryptToKey(devConfig.getDevPublicKey(),
 				plaintext);
 		String armoured = crypto.asciiArmour(ciphertext, LINE_LENGTH);
@@ -111,15 +109,17 @@ class DevReporterImpl implements DevReporter, EventListener {
 		LOG.info("Sending reports to developers");
 		for (File f : reports) {
 			OutputStream out = null;
+			InputStream in = null;
 			try {
 				Socket s = connectToDevelopers();
-				out = getOutputStream(s);
-				InputStream in = new FileInputStream(f);
-				copyAndClose(in, out);
-				if (!f.delete()) LOG.warning("Failed to delete report");
+				out = IoUtils.getOutputStream(s);
+				in = new FileInputStream(f);
+				IoUtils.copyAndClose(in, out);
+				f.delete();
 			} catch (IOException e) {
 				LOG.log(WARNING, "Failed to send reports", e);
 				tryToClose(out, LOG, WARNING);
+				tryToClose(in, LOG, WARNING);
 				return;
 			}
 		}

bramble-core/src/main/java/org/briarproject/bramble/socks/SocksSocket.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.socks;
 
+import org.briarproject.bramble.util.ByteUtils;
 import org.briarproject.bramble.util.IoUtils;
 
 import java.io.IOException;
@@ -11,9 +12,6 @@ import java.net.Socket;
 import java.net.SocketAddress;
 import java.util.Arrays;
 
-import static org.briarproject.bramble.util.ByteUtils.writeUint16;
-import static org.briarproject.bramble.util.IoUtils.read;
-
 class SocksSocket extends Socket {
 
 	private static final String[] ERRORS = {
@@ -28,7 +26,6 @@ class SocksSocket extends Socket {
 			"Address type not supported"
 	};
 
-	@SuppressWarnings("MismatchedReadAndWriteOfArray")
 	private static final byte[] UNSPECIFIED_ADDRESS = new byte[4];
 
 	private final SocketAddress proxy;
@@ -91,7 +88,7 @@ class SocksSocket extends Socket {
 
 	private void receiveMethodResponse(InputStream in) throws IOException {
 		byte[] methodResponse = new byte[2];
-		read(in, methodResponse);
+		IoUtils.read(in, methodResponse);
 		byte version = methodResponse[0];
 		byte method = methodResponse[1];
 		if (version != 5)
@@ -111,14 +108,14 @@ class SocksSocket extends Socket {
 		connectRequest[4] = (byte) host.length(); // Length of domain name
 		for (int i = 0; i < host.length(); i++)
 			connectRequest[5 + i] = (byte) host.charAt(i);
-		writeUint16(port, connectRequest, connectRequest.length - 2);
+		ByteUtils.writeUint16(port, connectRequest, connectRequest.length - 2);
 		out.write(connectRequest);
 		out.flush();
 	}
 
 	private void receiveConnectResponse(InputStream in) throws IOException {
 		byte[] connectResponse = new byte[4];
-		read(in, connectResponse);
+		IoUtils.read(in, connectResponse);
 		int version = connectResponse[0] & 0xFF;
 		int reply = connectResponse[1] & 0xFF;
 		int addressType = connectResponse[3] & 0xFF;
@@ -129,9 +126,9 @@ class SocksSocket extends Socket {
 				throw new IOException("Connection failed: " + ERRORS[reply]);
 			else throw new IOException("Connection failed: " + reply);
 		}
-		if (addressType == 1) read(in, new byte[4]); // IPv4
-		else if (addressType == 4) read(in, new byte[16]); // IPv6
+		if (addressType == 1) IoUtils.read(in, new byte[4]); // IPv4
+		else if (addressType == 4) IoUtils.read(in, new byte[16]); // IPv6
 		else throw new IOException("Unsupported address type: " + addressType);
-		read(in, new byte[2]); // Port number
+		IoUtils.read(in, new byte[2]); // Port number
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/socks/SocksSocketFactory.java

@@ -45,7 +45,7 @@ class SocksSocketFactory extends SocketFactory {
 
 	@Override
 	public Socket createSocket(InetAddress address, int port,
-			InetAddress localAddress, int localPort) {
+			InetAddress localAddress, int localPort) throws IOException {
 		throw new UnsupportedOperationException();
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -39,7 +39,6 @@ import javax.annotation.concurrent.ThreadSafe;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
@@ -56,7 +55,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 class DuplexOutgoingSession implements SyncSession, EventListener {
 
 	private static final Logger LOG =
-			getLogger(DuplexOutgoingSession.class.getName());
+			Logger.getLogger(DuplexOutgoingSession.class.getName());
 
 	private static final ThrowingRunnable<IOException> CLOSE = () -> {
 	};

bramble-core/src/main/java/org/briarproject/bramble/sync/GroupFactoryImpl.java

@@ -6,6 +6,8 @@ import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupFactory;
 import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.util.ByteUtils;
+import org.briarproject.bramble.util.StringUtils;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
@@ -13,8 +15,6 @@ import javax.inject.Inject;
 import static org.briarproject.bramble.api.sync.Group.FORMAT_VERSION;
 import static org.briarproject.bramble.api.sync.GroupId.LABEL;
 import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.writeUint32;
-import static org.briarproject.bramble.util.StringUtils.toUtf8;
 
 @Immutable
 @NotNullByDefault
@@ -33,9 +33,10 @@ class GroupFactoryImpl implements GroupFactory {
 	@Override
 	public Group createGroup(ClientId c, int majorVersion, byte[] descriptor) {
 		byte[] majorVersionBytes = new byte[INT_32_BYTES];
-		writeUint32(majorVersion, majorVersionBytes, 0);
+		ByteUtils.writeUint32(majorVersion, majorVersionBytes, 0);
 		byte[] hash = crypto.hash(LABEL, FORMAT_VERSION_BYTES,
-				toUtf8(c.getString()), majorVersionBytes, descriptor);
+				StringUtils.toUtf8(c.getString()), majorVersionBytes,
+				descriptor);
 		return new Group(new GroupId(hash), c, majorVersion, descriptor);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/IncomingSession.java

@@ -26,7 +26,6 @@ import java.util.logging.Logger;
 import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
@@ -38,7 +37,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 class IncomingSession implements SyncSession, EventListener {
 
 	private static final Logger LOG =
-			getLogger(IncomingSession.class.getName());
+			Logger.getLogger(IncomingSession.class.getName());
 
 	private final DatabaseComponent db;
 	private final Executor dbExecutor;

bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java

@@ -7,11 +7,11 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.util.ByteUtils;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.sync.Message.FORMAT_VERSION;
 import static org.briarproject.bramble.api.sync.MessageId.BLOCK_LABEL;
 import static org.briarproject.bramble.api.sync.MessageId.ID_LABEL;
@@ -19,8 +19,6 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_L
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.readUint64;
-import static org.briarproject.bramble.util.ByteUtils.writeUint64;
 
 @Immutable
 @NotNullByDefault
@@ -49,7 +47,7 @@ class MessageFactoryImpl implements MessageFactory {
 		// There's only one block, so the root hash is the hash of the block
 		byte[] rootHash = crypto.hash(BLOCK_LABEL, FORMAT_VERSION_BYTES, body);
 		byte[] timeBytes = new byte[INT_64_BYTES];
-		writeUint64(timestamp, timeBytes, 0);
+		ByteUtils.writeUint64(timestamp, timeBytes, 0);
 		byte[] idHash = crypto.hash(ID_LABEL, FORMAT_VERSION_BYTES,
 				g.getBytes(), timeBytes, rootHash);
 		return new MessageId(idHash);
@@ -62,11 +60,11 @@ class MessageFactoryImpl implements MessageFactory {
 		if (raw.length > MAX_MESSAGE_LENGTH)
 			throw new IllegalArgumentException();
 		byte[] groupId = new byte[UniqueId.LENGTH];
-		arraycopy(raw, 0, groupId, 0, UniqueId.LENGTH);
+		System.arraycopy(raw, 0, groupId, 0, UniqueId.LENGTH);
 		GroupId g = new GroupId(groupId);
-		long timestamp = readUint64(raw, UniqueId.LENGTH);
+		long timestamp = ByteUtils.readUint64(raw, UniqueId.LENGTH);
 		byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
-		arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
+		System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
 		MessageId id = getMessageId(g, timestamp, body);
 		return new Message(id, g, timestamp, body);
 	}
@@ -75,9 +73,9 @@ class MessageFactoryImpl implements MessageFactory {
 	public byte[] getRawMessage(Message m) {
 		byte[] body = m.getBody();
 		byte[] raw = new byte[MESSAGE_HEADER_LENGTH + body.length];
-		arraycopy(m.getGroupId().getBytes(), 0, raw, 0, UniqueId.LENGTH);
-		writeUint64(m.getTimestamp(), raw, UniqueId.LENGTH);
-		arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
+		System.arraycopy(m.getGroupId().getBytes(), 0, raw, 0, UniqueId.LENGTH);
+		ByteUtils.writeUint64(m.getTimestamp(), raw, UniqueId.LENGTH);
+		System.arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
 		return raw;
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/SimplexOutgoingSession.java

@@ -29,7 +29,6 @@ import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
@@ -45,7 +44,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 class SimplexOutgoingSession implements SyncSession, EventListener {
 
 	private static final Logger LOG =
-			getLogger(SimplexOutgoingSession.class.getName());
+			Logger.getLogger(SimplexOutgoingSession.class.getName());
 
 	private static final ThrowingRunnable<IOException> CLOSE = () -> {
 	};

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordReaderImpl.java

@@ -12,6 +12,7 @@ import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
 import org.briarproject.bramble.api.sync.Request;
 import org.briarproject.bramble.api.sync.SyncRecordReader;
+import org.briarproject.bramble.util.ByteUtils;
 
 import java.io.EOFException;
 import java.io.IOException;
@@ -21,14 +22,12 @@ import java.util.List;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.sync.RecordTypes.ACK;
 import static org.briarproject.bramble.api.sync.RecordTypes.MESSAGE;
 import static org.briarproject.bramble.api.sync.RecordTypes.OFFER;
 import static org.briarproject.bramble.api.sync.RecordTypes.REQUEST;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.util.ByteUtils.readUint64;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -108,7 +107,7 @@ class SyncRecordReaderImpl implements SyncRecordReader {
 		List<MessageId> ids = new ArrayList<>(payload.length / UniqueId.LENGTH);
 		for (int off = 0; off < payload.length; off += UniqueId.LENGTH) {
 			byte[] id = new byte[UniqueId.LENGTH];
-			arraycopy(payload, off, id, 0, UniqueId.LENGTH);
+			System.arraycopy(payload, off, id, 0, UniqueId.LENGTH);
 			ids.add(new MessageId(id));
 		}
 		nextRecord = null;
@@ -128,7 +127,7 @@ class SyncRecordReaderImpl implements SyncRecordReader {
 		if (payload.length <= MESSAGE_HEADER_LENGTH)
 			throw new FormatException();
 		// Validate timestamp
-		long timestamp = readUint64(payload, UniqueId.LENGTH);
+		long timestamp = ByteUtils.readUint64(payload, UniqueId.LENGTH);
 		if (timestamp < 0) throw new FormatException();
 		nextRecord = null;
 		return messageFactory.createMessage(payload);

bramble-core/src/main/java/org/briarproject/bramble/sync/validation/ValidationManagerImpl.java

@@ -40,7 +40,6 @@ import javax.inject.Inject;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.INVALID;
 import static org.briarproject.bramble.api.sync.validation.MessageState.PENDING;
@@ -52,7 +51,7 @@ class ValidationManagerImpl implements ValidationManager, Service,
 		EventListener {
 
 	private static final Logger LOG =
-			getLogger(ValidationManagerImpl.class.getName());
+			Logger.getLogger(ValidationManagerImpl.class.getName());
 
 	private final DatabaseComponent db;
 	private final Executor dbExecutor, validationExecutor;

bramble-core/src/main/java/org/briarproject/bramble/system/UnixSecureRandomProvider.java

@@ -14,7 +14,6 @@ import javax.annotation.concurrent.Immutable;
 
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @Immutable
@@ -44,16 +43,15 @@ class UnixSecureRandomProvider extends AbstractSecureRandomProvider {
 	}
 
 	protected void writeSeed() {
-		DataOutputStream out = null;
 		try {
-			out = new DataOutputStream(new FileOutputStream(outputDevice));
+			DataOutputStream out = new DataOutputStream(
+					new FileOutputStream(outputDevice));
 			writeToEntropyPool(out);
 			out.flush();
+			out.close();
 		} catch (IOException e) {
 			// On some devices /dev/urandom isn't writable - this isn't fatal
 			logException(LOG, WARNING, e);
-		} finally {
-			tryToClose(out, LOG, WARNING);
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/system/UnixSecureRandomSpi.java

@@ -11,7 +11,6 @@ import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 public class UnixSecureRandomSpi extends SecureRandomSpi {
@@ -35,16 +34,15 @@ public class UnixSecureRandomSpi extends SecureRandomSpi {
 
 	@Override
 	protected void engineSetSeed(byte[] seed) {
-		DataOutputStream out = null;
 		try {
-			out = new DataOutputStream(new FileOutputStream(outputDevice));
+			DataOutputStream out = new DataOutputStream(
+					new FileOutputStream(outputDevice));
 			out.write(seed);
 			out.flush();
+			out.close();
 		} catch (IOException e) {
 			// On some devices /dev/urandom isn't writable - this isn't fatal
 			logException(LOG, WARNING, e);
-		} finally {
-			tryToClose(out, LOG, WARNING);
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/transport/KeyManagerImpl.java

@@ -34,13 +34,13 @@ import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.INFO;
-import static java.util.logging.Logger.getLogger;
 
 @ThreadSafe
 @NotNullByDefault
 class KeyManagerImpl implements KeyManager, Service, EventListener {
 
-	private static final Logger LOG = getLogger(KeyManagerImpl.class.getName());
+	private static final Logger LOG =
+			Logger.getLogger(KeyManagerImpl.class.getName());
 
 	private final DatabaseComponent db;
 	private final Executor dbExecutor;

bramble-core/src/main/java/org/briarproject/bramble/transport/ReorderingWindow.java

@@ -3,12 +3,11 @@ package org.briarproject.bramble.transport;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.util.ByteUtils.MAX_32_BIT_UNSIGNED;
 
 @NotThreadSafe
@@ -65,8 +64,8 @@ class ReorderingWindow {
 		while (seen[slide]) slide++;
 		// If the window doesn't need to slide, return
 		if (slide == 0) {
-			List<Long> added = emptyList();
-			List<Long> removed = singletonList(index);
+			List<Long> added = Collections.emptyList();
+			List<Long> removed = Collections.singletonList(index);
 			return new Change(added, removed);
 		}
 		// Record the elements that will be added and removed