More static imports.

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

@@ -9,7 +9,6 @@ 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;
@@ -18,6 +17,7 @@ import javax.annotation.Nullable;
 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 {
@@ -99,7 +99,7 @@ class AndroidAccountManager extends AccountManagerImpl
 			for (File child : children) {
 				String name = child.getName();
 				if (!name.equals("lib") && !name.equals("shared_prefs")) {
-					IoUtils.deleteFileOrDir(child);
+					deleteFileOrDir(child);
 				}
 			}
 		}

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

@@ -24,7 +24,6 @@ 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;
@@ -48,6 +47,7 @@ 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;
@@ -260,7 +260,7 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 			appContext.unregisterReceiver(receiver);
 		}
 		// Shuffle the addresses so we don't always try the same one first
-		Collections.shuffle(addresses);
+		shuffle(addresses);
 		return addresses;
 	}
 

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

@@ -1,7 +1,6 @@
 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;
@@ -26,6 +25,7 @@ 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
@@ -104,7 +104,7 @@ public class AndroidTorPluginFactory implements DuplexPluginFactory {
 			return null;
 		}
 		// Use position-independent executable for SDK >= 16
-		if (Build.VERSION.SDK_INT >= 16) architecture += "_pie";
+		if (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/AndroidSecureRandomProvider.java

@@ -8,7 +8,6 @@ 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;
@@ -23,6 +22,9 @@ 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
@@ -45,8 +47,8 @@ class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 		out.writeInt(android.os.Process.myPid());
 		out.writeInt(android.os.Process.myTid());
 		out.writeInt(android.os.Process.myUid());
-		if (Build.FINGERPRINT != null) out.writeUTF(Build.FINGERPRINT);
+		if (FINGERPRINT != null) out.writeUTF(FINGERPRINT);
-		if (Build.SERIAL != null) out.writeUTF(Build.SERIAL);
+		if (SERIAL != null) out.writeUTF(SERIAL);
 		ContentResolver contentResolver = appContext.getContentResolver();
 		String id = Settings.Secure.getString(contentResolver, ANDROID_ID);
 		if (id != null) out.writeUTF(id);
@@ -74,15 +76,13 @@ class AndroidSecureRandomProvider extends UnixSecureRandomProvider {
 		// Silence strict mode
 		StrictMode.ThreadPolicy tp = StrictMode.allowThreadDiskWrites();
 		super.writeSeed();
-		if (Build.VERSION.SDK_INT >= 16 && Build.VERSION.SDK_INT <= 18)
+		if (SDK_INT >= 16 && SDK_INT <= 18) applyOpenSslFix();
-			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(
+		byte[] seed = new UnixSecureRandomSpi().engineGenerateSeed(SEED_LENGTH);
-				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

@@ -3,17 +3,19 @@ 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 {
@@ -27,10 +29,10 @@ public class AndroidUtils {
 	public static Collection<String> getSupportedArchitectures() {
 		List<String> abis = new ArrayList<>();
 		if (SDK_INT >= 21) {
-			abis.addAll(Arrays.asList(Build.SUPPORTED_ABIS));
+			abis.addAll(asList(SUPPORTED_ABIS));
 		} else {
-			abis.add(Build.CPU_ABI);
+			abis.add(CPU_ABI);
-			if (Build.CPU_ABI2 != null) abis.add(Build.CPU_ABI2);
+			if (CPU_ABI2 != null) abis.add(CPU_ABI2);
 		}
 		return abis;
 	}

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

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

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

@@ -5,10 +5,11 @@ 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 {
@@ -23,7 +24,7 @@ public class BdfMessageContext {
 	}
 
 	public BdfMessageContext(BdfDictionary dictionary) {
-		this(dictionary, Collections.emptyList());
+		this(dictionary, emptyList());
 	}
 
 	public BdfDictionary getDictionary() {

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(Arrays.asList(items));
+		return new BdfList(asList(items));
 	}
 
 	public BdfList() {

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

@@ -3,11 +3,12 @@ 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.
  */
@@ -53,7 +54,7 @@ public class Transaction {
 	 * Returns any events attached to the transaction.
 	 */
 	public List<Event> getEvents() {
-		if (events == null) return Collections.emptyList();
+		if (events == null) return emptyList();
 		return events;
 	}
 

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

@@ -4,10 +4,11 @@ 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 {
@@ -22,7 +23,7 @@ public class MessageContext {
 	}
 
 	public MessageContext(Metadata metadata) {
-		this(metadata, Collections.emptyList());
+		this(metadata, emptyList());
 	}
 
 	public Metadata getMetadata() {

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

@@ -8,6 +8,7 @@ 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;
@@ -19,15 +20,15 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	public void testConstructors() {
 		assertEquals(Collections.<String, Object>emptyMap(),
 				new BdfDictionary());
-		assertEquals(Collections.singletonMap("foo", NULL_VALUE),
+		assertEquals(singletonMap("foo", NULL_VALUE),
-				new BdfDictionary(Collections.singletonMap("foo", NULL_VALUE)));
+				new BdfDictionary(singletonMap("foo", NULL_VALUE)));
 	}
 
 	@Test
 	public void testFactoryMethod() {
 		assertEquals(Collections.<String, Object>emptyMap(),
 				BdfDictionary.of());
-		assertEquals(Collections.singletonMap("foo", NULL_VALUE),
+		assertEquals(singletonMap("foo", NULL_VALUE),
 				BdfDictionary.of(new BdfEntry("foo", NULL_VALUE)));
 	}
 

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

@@ -5,9 +5,8 @@ import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.junit.Test;
 
-import java.util.Arrays;
+import static java.util.Arrays.asList;
-import java.util.Collections;
+import static java.util.Collections.emptyList;
-
 import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
@@ -16,15 +15,15 @@ public class BdfListTest extends BrambleTestCase {
 
 	@Test
 	public void testConstructors() {
-		assertEquals(Collections.emptyList(), new BdfList());
+		assertEquals(emptyList(), new BdfList());
-		assertEquals(Arrays.asList(1, 2, NULL_VALUE),
+		assertEquals(asList(1, 2, NULL_VALUE),
-				new BdfList(Arrays.asList(1, 2, NULL_VALUE)));
+				new BdfList(asList(1, 2, NULL_VALUE)));
 	}
 
 	@Test
 	public void testFactoryMethod() {
-		assertEquals(Collections.emptyList(), BdfList.of());
+		assertEquals(emptyList(), BdfList.of());
-		assertEquals(Arrays.asList(1, 2, NULL_VALUE),
+		assertEquals(asList(1, 2, NULL_VALUE),
 				BdfList.of(1, 2, NULL_VALUE));
 	}
 

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

@@ -12,12 +12,10 @@ 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;
@@ -25,6 +23,7 @@ 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;
@@ -33,6 +32,7 @@ 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 {
@@ -48,7 +48,7 @@ public class TestUtils {
 	}
 
 	public static void deleteTestDirectory(File testDir) {
-		IoUtils.deleteFileOrDir(testDir);
+		deleteFileOrDir(testDir);
 		testDir.getParentFile().delete(); // Delete if empty
 	}
 
@@ -145,7 +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());
-		Collections.sort(sorted);
+		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/account/AccountManagerImpl.java

@@ -8,7 +8,6 @@ import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 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;
@@ -23,6 +22,7 @@ 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;
@@ -182,8 +182,8 @@ class AccountManagerImpl implements AccountManager {
 	public void deleteAccount() {
 		synchronized (stateChangeLock) {
 			LOG.info("Deleting account");
-			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseKeyDirectory());
+			deleteFileOrDir(databaseConfig.getDatabaseKeyDirectory());
-			IoUtils.deleteFileOrDir(databaseConfig.getDatabaseDirectory());
+			deleteFileOrDir(databaseConfig.getDatabaseDirectory());
 			databaseKey = null;
 		}
 	}

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

@@ -28,6 +28,7 @@ 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;
@@ -190,7 +191,7 @@ class CryptoComponentImpl implements CryptoComponent {
 		PrivateKey ourPriv = ourKeyPair.getPrivate();
 		byte[][] hashInputs = new byte[inputs.length + 1][];
 		hashInputs[0] = performRawKeyAgreement(ourPriv, theirPublicKey);
-		System.arraycopy(inputs, 0, hashInputs, 1, inputs.length);
+		arraycopy(inputs, 0, hashInputs, 1, inputs.length);
 		byte[] hash = hash(label, hashInputs);
 		if (hash.length != SecretKey.LENGTH) throw new IllegalStateException();
 		return new SecretKey(hash);
@@ -299,13 +300,13 @@ class CryptoComponentImpl implements CryptoComponent {
 		output[outputOff] = PBKDF_FORMAT_SCRYPT;
 		outputOff++;
 		// Salt
-		System.arraycopy(salt, 0, output, outputOff, salt.length);
+		arraycopy(salt, 0, output, outputOff, salt.length);
 		outputOff += salt.length;
 		// Cost parameter
 		writeUint32(cost, output, outputOff);
 		outputOff += INT_32_BYTES;
 		// IV
-		System.arraycopy(iv, 0, output, outputOff, iv.length);
+		arraycopy(iv, 0, output, outputOff, iv.length);
 		outputOff += iv.length;
 		// Initialise the cipher and encrypt the plaintext
 		try {
@@ -335,7 +336,7 @@ class CryptoComponentImpl implements CryptoComponent {
 			return null; // Unknown format
 		// Salt
 		byte[] salt = new byte[PBKDF_SALT_BYTES];
-		System.arraycopy(input, inputOff, salt, 0, salt.length);
+		arraycopy(input, inputOff, salt, 0, salt.length);
 		inputOff += salt.length;
 		// Cost parameter
 		long cost = readUint32(input, inputOff);
@@ -344,7 +345,7 @@ class CryptoComponentImpl implements CryptoComponent {
 			return null; // Invalid cost parameter
 		// IV
 		byte[] iv = new byte[STORAGE_IV_BYTES];
-		System.arraycopy(input, inputOff, iv, 0, iv.length);
+		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

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

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

@@ -8,6 +8,7 @@ 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 {
@@ -24,7 +25,7 @@ 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];
-		System.arraycopy(hash, 0, commitment, 0, COMMIT_LENGTH);
+		arraycopy(hash, 0, commitment, 0, COMMIT_LENGTH);
 		return commitment;
 	}
 

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

@@ -16,6 +16,7 @@ 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;
@@ -56,12 +57,12 @@ 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];
-		System.arraycopy(encodedKey, 1, xBytes, 0, bytesPerInt);
+		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];
-		System.arraycopy(encodedKey, 1 + bytesPerInt, yBytes, 0, bytesPerInt);
+		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

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

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

@@ -13,6 +13,7 @@ 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;
@@ -131,7 +132,7 @@ class StreamDecrypterImpl implements StreamDecrypter {
 		}
 		// Extract the nonce
 		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
-		System.arraycopy(streamHeaderCiphertext, 0, streamHeaderNonce, 0,
+		arraycopy(streamHeaderCiphertext, 0, streamHeaderNonce, 0,
 				STREAM_HEADER_NONCE_LENGTH);
 		// Decrypt and authenticate the stream header
 		try {
@@ -155,7 +156,7 @@ class StreamDecrypterImpl implements StreamDecrypter {
 		if (receivedStreamNumber != streamNumber) throw new FormatException();
 		// Extract the frame key
 		byte[] frameKeyBytes = new byte[SecretKey.LENGTH];
-		System.arraycopy(streamHeaderPlaintext, INT_16_BYTES + INT_64_BYTES,
+		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

@@ -11,6 +11,7 @@ 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;
@@ -89,7 +90,7 @@ class StreamEncrypterImpl implements StreamEncrypter {
 			throw new RuntimeException(badCipher);
 		}
 		// Combine the payload and padding
-		System.arraycopy(payload, 0, framePlaintext, 0, payloadLength);
+		arraycopy(payload, 0, framePlaintext, 0, payloadLength);
 		for (int i = 0; i < paddingLength; i++)
 			framePlaintext[payloadLength + i] = 0;
 		// Encrypt and authenticate the payload and padding
@@ -121,10 +122,10 @@ class StreamEncrypterImpl implements StreamEncrypter {
 		byte[] streamHeaderPlaintext = new byte[STREAM_HEADER_PLAINTEXT_LENGTH];
 		writeUint16(PROTOCOL_VERSION, streamHeaderPlaintext, 0);
 		writeUint64(streamNumber, streamHeaderPlaintext, INT_16_BYTES);
-		System.arraycopy(frameKey.getBytes(), 0, streamHeaderPlaintext,
+		arraycopy(frameKey.getBytes(), 0, streamHeaderPlaintext,
 				INT_16_BYTES + INT_64_BYTES, SecretKey.LENGTH);
 		byte[] streamHeaderCiphertext = new byte[STREAM_HEADER_LENGTH];
-		System.arraycopy(streamHeaderNonce, 0, streamHeaderCiphertext, 0,
+		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

@@ -12,6 +12,7 @@ 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;
@@ -134,6 +135,6 @@ class TransportCryptoImpl implements TransportCrypto {
 		byte[] mac = new byte[macLength];
 		prf.doFinal(mac, 0);
 		// The output is the first TAG_LENGTH bytes of the MAC
-		System.arraycopy(mac, 0, tag, 0, TAG_LENGTH);
+		arraycopy(mac, 0, tag, 0, TAG_LENGTH);
 	}
 }

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

@@ -61,7 +61,6 @@ 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;
@@ -72,6 +71,7 @@ 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;
@@ -899,7 +899,7 @@ 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 = Collections.singletonList(c);
+		List<ContactId> affected = singletonList(c);
 		transaction.attach(new GroupVisibilityUpdatedEvent(affected));
 	}
 

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

@@ -38,9 +38,7 @@ 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;
@@ -55,8 +53,12 @@ import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 
+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;
@@ -424,7 +426,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
 	List<Migration<Connection>> getMigrations() {
-		return Arrays.asList(
+		return asList(
 				new Migration38_39(),
 				new Migration39_40(),
 				new Migration40_41(dbTypes)
@@ -1536,7 +1538,7 @@ 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];
-			System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
+			arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
 			return new Message(m, g, timestamp, body);
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
@@ -1596,7 +1598,7 @@ 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 Collections.emptySet();
+				if (intersection.isEmpty()) return emptySet();
 			}
 			if (intersection == null) throw new AssertionError();
 			return intersection;
@@ -1645,7 +1647,7 @@ 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 Collections.emptyMap();
+		if (matches.isEmpty()) return 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));
@@ -2395,7 +2397,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 				}
 				ps.close();
 			}
-			if (notRemoved.isEmpty()) return Collections.emptyMap();
+			if (notRemoved.isEmpty()) return 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/plugin/ConnectionRegistryImpl.java

@@ -13,7 +13,6 @@ 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;
@@ -24,6 +23,7 @@ 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;
 
@@ -104,7 +104,7 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 		lock.lock();
 		try {
 			Multiset<ContactId> m = connections.get(t);
-			if (m == null) return Collections.emptyList();
+			if (m == null) return 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/tcp/WanTcpPlugin.java

@@ -10,11 +10,12 @@ 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
@@ -80,8 +81,7 @@ class WanTcpPlugin extends TcpPlugin {
 	protected List<InetSocketAddress> getRemoteSocketAddresses(
 			TransportProperties p) {
 		InetSocketAddress parsed = parseSocketAddress(p.get(PROP_IP_PORT));
-		if (parsed == null) return Collections.emptyList();
+		return parsed == null ? emptyList() : singletonList(parsed);
-		return Collections.singletonList(parsed);
 	}
 
 	@Override

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

@@ -42,9 +42,7 @@ 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;
@@ -58,6 +56,9 @@ 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;
@@ -252,11 +253,11 @@ 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(Collections.singletonList(OWNER));
+			controlConnection.resetConf(singletonList(OWNER));
 			running = true;
 			// Register to receive events from the Tor process
 			controlConnection.setEventHandler(this);
-			controlConnection.setEvents(Arrays.asList(EVENTS));
+			controlConnection.setEvents(asList(EVENTS));
 			// Check whether Tor has already bootstrapped
 			String phase = controlConnection.getInfo("status/bootstrap-phase");
 			if (phase != null && phase.contains("PROGRESS=100")) {
@@ -411,8 +412,7 @@ 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 =
+		Map<Integer, String> portLines = singletonMap(80, "127.0.0.1:" + port);
-				Collections.singletonMap(80, "127.0.0.1:" + port);
 		Map<String, String> response;
 		try {
 			// Use the control connection to set up the hidden service

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

@@ -8,6 +8,8 @@ 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 {
@@ -44,7 +46,7 @@ class ReceiverInputStream extends InputStream {
 		while (length == 0) if (!receive()) return -1;
 		if (data == null) throw new AssertionError();
 		len = Math.min(len, length);
-		System.arraycopy(data.getBuffer(), offset, b, off, len);
+		arraycopy(data.getBuffer(), offset, b, off, len);
 		offset += len;
 		length -= len;
 		return len;

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

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

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

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

@@ -1,7 +1,6 @@
 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;
@@ -17,6 +16,9 @@ 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 {
@@ -131,9 +133,9 @@ public class DevReportServer {
 			OutputStream out = null;
 			try {
 				socket.setSoTimeout(SOCKET_TIMEOUT_MS);
-				in = IoUtils.getInputStream(socket);
+				in = getInputStream(socket);
 				reportDir.mkdirs();
-				reportFile = File.createTempFile(FILE_PREFIX, FILE_SUFFIX,
+				reportFile = createTempFile(FILE_PREFIX, FILE_SUFFIX,
 						reportDir);
 				out = new FileOutputStream(reportFile);
 				System.out.println("Saving report to " + reportFile);

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

@@ -12,6 +12,7 @@ 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 {
 
@@ -89,7 +90,7 @@ class SocksSocket extends Socket {
 
 	private void receiveMethodResponse(InputStream in) throws IOException {
 		byte[] methodResponse = new byte[2];
-		IoUtils.read(in, methodResponse);
+		read(in, methodResponse);
 		byte version = methodResponse[0];
 		byte method = methodResponse[1];
 		if (version != 5)
@@ -116,7 +117,7 @@ class SocksSocket extends Socket {
 
 	private void receiveConnectResponse(InputStream in) throws IOException {
 		byte[] connectResponse = new byte[4];
-		IoUtils.read(in, connectResponse);
+		read(in, connectResponse);
 		int version = connectResponse[0] & 0xFF;
 		int reply = connectResponse[1] & 0xFF;
 		int addressType = connectResponse[3] & 0xFF;
@@ -127,9 +128,9 @@ class SocksSocket extends Socket {
 				throw new IOException("Connection failed: " + ERRORS[reply]);
 			else throw new IOException("Connection failed: " + reply);
 		}
-		if (addressType == 1) IoUtils.read(in, new byte[4]); // IPv4
+		if (addressType == 1) read(in, new byte[4]); // IPv4
-		else if (addressType == 4) IoUtils.read(in, new byte[16]); // IPv6
+		else if (addressType == 4) read(in, new byte[16]); // IPv6
 		else throw new IOException("Unsupported address type: " + addressType);
-		IoUtils.read(in, new byte[2]); // Port number
+		read(in, new byte[2]); // Port number
 	}
 }

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

@@ -11,6 +11,7 @@ import org.briarproject.bramble.api.sync.MessageId;
 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;
@@ -61,11 +62,11 @@ class MessageFactoryImpl implements MessageFactory {
 		if (raw.length > MAX_MESSAGE_LENGTH)
 			throw new IllegalArgumentException();
 		byte[] groupId = new byte[UniqueId.LENGTH];
-		System.arraycopy(raw, 0, groupId, 0, UniqueId.LENGTH);
+		arraycopy(raw, 0, groupId, 0, UniqueId.LENGTH);
 		GroupId g = new GroupId(groupId);
 		long timestamp = readUint64(raw, UniqueId.LENGTH);
 		byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
-		System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
+		arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
 		MessageId id = getMessageId(g, timestamp, body);
 		return new Message(id, g, timestamp, body);
 	}
@@ -74,9 +75,9 @@ class MessageFactoryImpl implements MessageFactory {
 	public byte[] getRawMessage(Message m) {
 		byte[] body = m.getBody();
 		byte[] raw = new byte[MESSAGE_HEADER_LENGTH + body.length];
-		System.arraycopy(m.getGroupId().getBytes(), 0, raw, 0, UniqueId.LENGTH);
+		arraycopy(m.getGroupId().getBytes(), 0, raw, 0, UniqueId.LENGTH);
 		writeUint64(m.getTimestamp(), raw, UniqueId.LENGTH);
-		System.arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
+		arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
 		return raw;
 	}
 }

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

@@ -21,6 +21,7 @@ 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;
@@ -107,7 +108,7 @@ 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];
-			System.arraycopy(payload, off, id, 0, UniqueId.LENGTH);
+			arraycopy(payload, off, id, 0, UniqueId.LENGTH);
 			ids.add(new MessageId(id));
 		}
 		nextRecord = null;

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

@@ -3,11 +3,12 @@ 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
@@ -64,8 +65,8 @@ class ReorderingWindow {
 		while (seen[slide]) slide++;
 		// If the window doesn't need to slide, return
 		if (slide == 0) {
-			List<Long> added = Collections.emptyList();
+			List<Long> added = emptyList();
-			List<Long> removed = Collections.singletonList(index);
+			List<Long> removed = singletonList(index);
 			return new Change(added, removed);
 		}
 		// Record the elements that will be added and removed

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

@@ -8,6 +8,7 @@ import java.io.InputStream;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
+import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
 
 /**
@@ -51,7 +52,7 @@ class StreamReaderImpl extends InputStream {
 			readFrame();
 		}
 		len = Math.min(len, length);
-		System.arraycopy(payload, offset, b, off, len);
+		arraycopy(payload, offset, b, off, len);
 		offset += len;
 		length -= len;
 		return len;

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

@@ -9,6 +9,7 @@ import java.io.OutputStream;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
+import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
 
 /**
@@ -70,14 +71,14 @@ class StreamWriterImpl extends OutputStream implements StreamWriter {
 	public void write(byte[] b, int off, int len) throws IOException {
 		int available = payload.length - length;
 		while (available <= len) {
-			System.arraycopy(b, off, payload, length, available);
+			arraycopy(b, off, payload, length, available);
 			length += available;
 			writeFrame(false);
 			off += available;
 			len -= available;
 			available = payload.length - length;
 		}
-		System.arraycopy(b, off, payload, length, len);
+		arraycopy(b, off, payload, length, len);
 		length += len;
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/versioning/ClientVersioningManagerImpl.java

@@ -30,7 +30,6 @@ import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -45,6 +44,7 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import static java.util.Collections.emptyList;
+import static java.util.Collections.sort;
 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.Group.Visibility.VISIBLE;
@@ -134,7 +134,7 @@ class ClientVersioningManagerImpl implements ClientVersioningManager, Client,
 	@Override
 	public void startService() throws ServiceException {
 		List<ClientVersion> versions = new ArrayList<>(clients);
-		Collections.sort(versions);
+		sort(versions);
 		try {
 			db.transaction(false, txn -> {
 				if (updateClientVersions(txn, versions)) {
@@ -167,7 +167,7 @@ class ClientVersioningManagerImpl implements ClientVersioningManager, Client,
 		}
 		// Create and store the first local update
 		List<ClientVersion> versions = new ArrayList<>(clients);
-		Collections.sort(versions);
+		sort(versions);
 		storeFirstUpdate(txn, g.getId(), versions);
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/PoliteExecutorTest.java

@@ -3,13 +3,13 @@ package org.briarproject.bramble;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.junit.Test;
 
-import java.util.Arrays;
 import java.util.List;
 import java.util.Vector;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
 
+import static java.util.Arrays.asList;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
@@ -119,12 +119,12 @@ public class PoliteExecutorTest extends BrambleTestCase {
 	private List<Integer> ascendingOrder() {
 		Integer[] array = new Integer[TASKS];
 		for (int i = 0; i < TASKS; i++) array[i] = i;
-		return Arrays.asList(array);
+		return asList(array);
 	}
 
 	private List<Integer> descendingOrder() {
 		Integer[] array = new Integer[TASKS];
 		for (int i = 0; i < TASKS; i++) array[i] = TASKS - 1 - i;
-		return Arrays.asList(array);
+		return asList(array);
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/client/ClientHelperImplTest.java

@@ -30,11 +30,11 @@ import org.junit.Test;
 import java.io.ByteArrayOutputStream;
 import java.io.InputStream;
 import java.security.GeneralSecurityException;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Random;
 
+import static java.util.Collections.singletonMap;
 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.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
@@ -166,7 +166,7 @@ public class ClientHelperImplTest extends BrambleTestCase {
 		context.checking(new DbExpectations() {{
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getMessageMetadata(txn, groupId);
-			will(returnValue(Collections.singletonMap(messageId, metadata)));
+			will(returnValue(singletonMap(messageId, metadata)));
 			oneOf(metadataParser).parse(metadata);
 			will(returnValue(dictionary));
 		}});
@@ -190,7 +190,7 @@ public class ClientHelperImplTest extends BrambleTestCase {
 			oneOf(metadataEncoder).encode(query);
 			will(returnValue(queryMetadata));
 			oneOf(db).getMessageMetadata(txn, groupId, queryMetadata);
-			will(returnValue(Collections.singletonMap(messageId, metadata)));
+			will(returnValue(singletonMap(messageId, metadata)));
 			oneOf(metadataParser).parse(metadata);
 			will(returnValue(dictionary));
 		}});

bramble-core/src/test/java/org/briarproject/bramble/contact/ContactManagerImplTest.java

@@ -22,7 +22,6 @@ import org.junit.Test;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Random;
 
 import static java.util.Collections.emptyList;
@@ -98,7 +97,7 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	@Test
 	public void testGetContactByAuthor() throws Exception {
 		Transaction txn = new Transaction(null, true);
-		Collection<Contact> contacts = Collections.singleton(contact);
+		Collection<Contact> contacts = singletonList(contact);
 		context.checking(new DbExpectations() {{
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContactsByAuthorId(txn, remote.getId());
@@ -123,7 +122,7 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 	@Test(expected = NoSuchContactException.class)
 	public void testGetContactByUnknownLocalAuthor() throws Exception {
 		Transaction txn = new Transaction(null, true);
-		Collection<Contact> contacts = Collections.singleton(contact);
+		Collection<Contact> contacts = singletonList(contact);
 		context.checking(new DbExpectations() {{
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
 			oneOf(db).getContactsByAuthorId(txn, remote.getId());
@@ -135,7 +134,7 @@ public class ContactManagerImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testGetActiveContacts() throws Exception {
-		Collection<Contact> activeContacts = Collections.singletonList(contact);
+		Collection<Contact> activeContacts = singletonList(contact);
 		Collection<Contact> contacts = new ArrayList<>(activeContacts);
 		contacts.add(new Contact(new ContactId(3), remote, local, alias, true,
 				false));

bramble-core/src/test/java/org/briarproject/bramble/crypto/EllipticCurvePerformanceTest.java

@@ -33,10 +33,10 @@ import java.security.Provider;
 import java.security.SecureRandom;
 import java.security.Signature;
 import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 
+import static java.util.Arrays.asList;
+import static java.util.Collections.sort;
 import static net.i2p.crypto.eddsa.EdDSAEngine.SIGNATURE_ALGORITHM;
 
 // Not a JUnit test
@@ -45,9 +45,9 @@ public class EllipticCurvePerformanceTest {
 	private static final SecureRandom random = new SecureRandom();
 	private static final int SAMPLES = 50;
 	private static final int BYTES_TO_SIGN = 1024;
-	private static final List<String> SEC_NAMES = Arrays.asList(
+	private static final List<String> SEC_NAMES = asList(
 			"secp256k1", "secp256r1", "secp384r1", "secp521r1");
-	private static final List<String> BRAINPOOL_NAMES = Arrays.asList(
+	private static final List<String> BRAINPOOL_NAMES = asList(
 			"brainpoolp256r1", "brainpoolp384r1", "brainpoolp512r1");
 	private static final Provider ED_PROVIDER = new EdDSASecurityProvider();
 
@@ -184,7 +184,7 @@ public class EllipticCurvePerformanceTest {
 	private static long median(List<Long> list) {
 		int size = list.size();
 		if (size == 0) throw new IllegalArgumentException();
-		Collections.sort(list);
+		sort(list);
 		if (size % 2 == 1) return list.get(size / 2);
 		return list.get(size / 2 - 1) + list.get(size / 2) / 2;
 	}

bramble-core/src/test/java/org/briarproject/bramble/crypto/PseudoSecureRandom.java

@@ -4,6 +4,8 @@ import java.security.Provider;
 import java.security.SecureRandom;
 import java.security.SecureRandomSpi;
 
+import static java.lang.System.arraycopy;
+
 class PseudoSecureRandom extends SecureRandom {
 
 	private static final Provider PROVIDER = new PseudoSecureRandomProvider();
@@ -28,7 +30,7 @@ class PseudoSecureRandom extends SecureRandom {
 		@Override
 		protected void engineNextBytes(byte[] b) {
 			byte[] random = pseudoRandom.nextBytes(b.length);
-			System.arraycopy(random, 0, b, 0, b.length);
+			arraycopy(random, 0, b, 0, b.length);
 		}
 
 		@Override

bramble-core/src/test/java/org/briarproject/bramble/crypto/StreamDecrypterImplTest.java

@@ -8,6 +8,7 @@ import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 
+import static java.lang.System.arraycopy;
 import static junit.framework.Assert.assertEquals;
 import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_HEADER_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAC_LENGTH;
@@ -287,7 +288,7 @@ public class StreamDecrypterImplTest extends BrambleTestCase {
 	private static void assertArrayStartsWith(byte[] expected, byte[] actual,
 			int len) {
 		byte[] prefix = new byte[len];
-		System.arraycopy(actual, 0, prefix, 0, len);
+		arraycopy(actual, 0, prefix, 0, len);
 		assertArrayEquals(expected, prefix);
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/crypto/TestAuthenticatedCipher.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.security.GeneralSecurityException;
 
+import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAC_LENGTH;
 
 @NotNullByDefault
@@ -22,7 +23,7 @@ class TestAuthenticatedCipher implements AuthenticatedCipher {
 	public int process(byte[] input, int inputOff, int len, byte[] output,
 			int outputOff) throws GeneralSecurityException {
 		if (encrypt) {
-			System.arraycopy(input, inputOff, output, outputOff, len);
+			arraycopy(input, inputOff, output, outputOff, len);
 			for (int i = 0; i < MAC_LENGTH; i++)
 				output[outputOff + len + i] = 0;
 			return len + MAC_LENGTH;
@@ -30,8 +31,7 @@ class TestAuthenticatedCipher implements AuthenticatedCipher {
 			for (int i = 0; i < MAC_LENGTH; i++)
 				if (input[inputOff + len - MAC_LENGTH + i] != 0)
 					throw new GeneralSecurityException();
-			System.arraycopy(input, inputOff, output, outputOff,
+			arraycopy(input, inputOff, output, outputOff, len - MAC_LENGTH);
-					len - MAC_LENGTH);
 			return len - MAC_LENGTH;
 		}
 	}

bramble-core/src/test/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipherTest.java

@@ -7,6 +7,7 @@ import org.junit.Test;
 import java.security.GeneralSecurityException;
 import java.util.Random;
 
+import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.util.StringUtils.fromHexString;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
@@ -74,7 +75,7 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 		AuthenticatedCipher cipher = new XSalsa20Poly1305AuthenticatedCipher();
 		cipher.init(false, k, TEST_IV);
 		byte[] input = new byte[cipher.getMacBytes() - 1];
-		System.arraycopy(TEST_CIPHERTEXT, 0, input, 0, input.length);
+		arraycopy(TEST_CIPHERTEXT, 0, input, 0, input.length);
 		byte[] output = new byte[TEST_PLAINTEXT.length];
 		cipher.process(input, 0, input.length, output, 0);
 	}
@@ -85,7 +86,7 @@ public class XSalsa20Poly1305AuthenticatedCipherTest extends BrambleTestCase {
 		AuthenticatedCipher cipher = new XSalsa20Poly1305AuthenticatedCipher();
 		cipher.init(false, k, TEST_IV);
 		byte[] input = new byte[TEST_CIPHERTEXT.length];
-		System.arraycopy(TEST_CIPHERTEXT, 0, input, 0, TEST_CIPHERTEXT.length);
+		arraycopy(TEST_CIPHERTEXT, 0, input, 0, TEST_CIPHERTEXT.length);
 		input[new Random().nextInt(TEST_CIPHERTEXT.length)] ^= 0xFF;
 		byte[] output = new byte[TEST_PLAINTEXT.length];
 		cipher.process(input, 0, input.length, output, 0);

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -37,7 +37,6 @@ import org.junit.Test;
 import java.io.File;
 import java.sql.Connection;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -47,6 +46,7 @@ import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
 
+import static java.util.Arrays.asList;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonList;
@@ -399,10 +399,10 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Both message IDs should be returned
 		Collection<MessageId> ids = db.getMessagesToAck(txn, contactId, 1234);
-		assertEquals(Arrays.asList(messageId, messageId1), ids);
+		assertEquals(asList(messageId, messageId1), ids);
 
 		// Remove both message IDs
-		db.lowerAckFlag(txn, contactId, Arrays.asList(messageId, messageId1));
+		db.lowerAckFlag(txn, contactId, asList(messageId, messageId1));
 
 		// Both message IDs should have been removed
 		assertEquals(emptyList(), db.getMessagesToAck(txn,
@@ -414,7 +414,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Both message IDs should be returned
 		ids = db.getMessagesToAck(txn, contactId, 1234);
-		assertEquals(Arrays.asList(messageId, messageId1), ids);
+		assertEquals(asList(messageId, messageId1), ids);
 
 		db.commitTransaction(txn);
 		db.close();

bramble-core/src/test/java/org/briarproject/bramble/identity/IdentityManagerImplTest.java

@@ -17,8 +17,8 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.util.Collection;
-import java.util.Collections;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
 import static org.junit.Assert.assertEquals;
 
@@ -34,7 +34,7 @@ public class IdentityManagerImplTest extends BrambleMockTestCase {
 	private final Transaction txn = new Transaction(null, false);
 	private final LocalAuthor localAuthor = getLocalAuthor();
 	private final Collection<LocalAuthor> localAuthors =
-			Collections.singletonList(localAuthor);
+			singletonList(localAuthor);
 	private final String authorName = localAuthor.getName();
 	private final KeyPair keyPair = new KeyPair(publicKey, privateKey);
 	private final byte[] publicKeyBytes = localAuthor.getPublicKey();

bramble-core/src/test/java/org/briarproject/bramble/plugin/ConnectionRegistryImplTest.java

@@ -14,9 +14,10 @@ import org.jmock.Mockery;
 import org.junit.Test;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.NoSuchElementException;
 
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -52,38 +53,31 @@ public class ConnectionRegistryImplTest extends BrambleTestCase {
 		ConnectionRegistry c = new ConnectionRegistryImpl(eventBus);
 
 		// The registry should be empty
-		assertEquals(Collections.emptyList(),
+		assertEquals(emptyList(), c.getConnectedContacts(transportId));
-				c.getConnectedContacts(transportId));
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-		assertEquals(Collections.emptyList(),
-				c.getConnectedContacts(transportId1));
 		// Check that a registered connection shows up - this should
 		// broadcast a ConnectionOpenedEvent and a ContactConnectedEvent
 		c.registerConnection(contactId, transportId, true);
-		assertEquals(Collections.singletonList(contactId),
+		assertEquals(singletonList(contactId),
 				c.getConnectedContacts(transportId));
-		assertEquals(Collections.emptyList(),
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-				c.getConnectedContacts(transportId1));
 		// Register an identical connection - this should broadcast a
 		// ConnectionOpenedEvent and lookup should be unaffected
 		c.registerConnection(contactId, transportId, true);
-		assertEquals(Collections.singletonList(contactId),
+		assertEquals(singletonList(contactId),
 				c.getConnectedContacts(transportId));
-		assertEquals(Collections.emptyList(),
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-				c.getConnectedContacts(transportId1));
 		// Unregister one of the connections - this should broadcast a
 		// ConnectionClosedEvent and lookup should be unaffected
 		c.unregisterConnection(contactId, transportId, true);
-		assertEquals(Collections.singletonList(contactId),
+		assertEquals(singletonList(contactId),
 				c.getConnectedContacts(transportId));
-		assertEquals(Collections.emptyList(),
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-				c.getConnectedContacts(transportId1));
 		// Unregister the other connection - this should broadcast a
 		// ConnectionClosedEvent and a ContactDisconnectedEvent
 		c.unregisterConnection(contactId, transportId, true);
-		assertEquals(Collections.emptyList(),
+		assertEquals(emptyList(), c.getConnectedContacts(transportId));
-				c.getConnectedContacts(transportId));
+		assertEquals(emptyList(), c.getConnectedContacts(transportId1));
-		assertEquals(Collections.emptyList(),
-				c.getConnectedContacts(transportId1));
 		// Try to unregister the connection again - exception should be thrown
 		try {
 			c.unregisterConnection(contactId, transportId, true);
@@ -101,7 +95,7 @@ public class ConnectionRegistryImplTest extends BrambleTestCase {
 		assertEquals(2, connected.size());
 		assertTrue(connected.contains(contactId));
 		assertTrue(connected.contains(contactId1));
-		assertEquals(Collections.singletonList(contactId1),
+		assertEquals(singletonList(contactId1),
 				c.getConnectedContacts(transportId1));
 		context.assertIsSatisfied();
 	}

bramble-core/src/test/java/org/briarproject/bramble/plugin/PluginManagerImplTest.java

@@ -22,11 +22,11 @@ import org.jmock.lib.concurrent.Synchroniser;
 import org.junit.Test;
 
 import java.security.SecureRandom;
-import java.util.Arrays;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 
+import static java.util.Arrays.asList;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
 
 public class PluginManagerImplTest extends BrambleTestCase {
@@ -84,8 +84,7 @@ public class PluginManagerImplTest extends BrambleTestCase {
 			// start()
 			// First simplex plugin
 			oneOf(pluginConfig).getSimplexFactories();
-			will(returnValue(Arrays.asList(simplexFactory,
+			will(returnValue(asList(simplexFactory, simplexFailFactory)));
-					simplexFailFactory)));
 			oneOf(simplexFactory).getId();
 			will(returnValue(simplexId));
 			oneOf(simplexFactory).createPlugin(with(any(
@@ -102,7 +101,7 @@ public class PluginManagerImplTest extends BrambleTestCase {
 			will(throwException(new PluginException()));
 			// First duplex plugin
 			oneOf(pluginConfig).getDuplexFactories();
-			will(returnValue(Arrays.asList(duplexFactory, duplexFailFactory)));
+			will(returnValue(asList(duplexFactory, duplexFailFactory)));
 			oneOf(duplexFactory).getId();
 			will(returnValue(duplexId));
 			oneOf(duplexFactory).createPlugin(with(any(

bramble-core/src/test/java/org/briarproject/bramble/plugin/tcp/LanTcpPluginTest.java

@@ -21,13 +21,14 @@ import java.net.InetSocketAddress;
 import java.net.NetworkInterface;
 import java.net.ServerSocket;
 import java.net.Socket;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import static java.net.NetworkInterface.getNetworkInterfaces;
+import static java.util.Collections.list;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_LAN;
@@ -327,9 +328,8 @@ public class LanTcpPluginTest extends BrambleTestCase {
 	}
 
 	private boolean systemHasLocalIpv4Address() throws Exception {
-		for (NetworkInterface i : Collections.list(
+		for (NetworkInterface i : list(getNetworkInterfaces())) {
-				NetworkInterface.getNetworkInterfaces())) {
+			for (InetAddress a : list(i.getInetAddresses())) {
-			for (InetAddress a : Collections.list(i.getInetAddresses())) {
 				if (a instanceof Inet4Address)
 					return a.isLinkLocalAddress() || a.isSiteLocalAddress();
 			}

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyManagerImplTest.java

@@ -25,12 +25,12 @@ import org.briarproject.bramble.test.DbExpectations;
 import org.jmock.Expectations;
 import org.junit.Test;
 
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
 import static java.util.Arrays.asList;
+import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_ID;
@@ -448,7 +448,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(contactGroup2));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup2.getId());
-			will(returnValue(Collections.emptyMap()));
+			will(returnValue(emptyMap()));
 			// Third contact: returns an update
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
 					MAJOR_VERSION, contact3);
@@ -514,7 +514,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			// There are no existing properties to merge with
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
-			will(returnValue(Collections.emptyMap()));
+			will(returnValue(emptyMap()));
 			// Store the new properties in the local group, version 1
 			expectStoreMessage(txn, localGroup.getId(), "foo",
 					fooPropertiesDict, 1, true, false);
@@ -526,7 +526,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(contactGroup));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
-			will(returnValue(Collections.emptyMap()));
+			will(returnValue(emptyMap()));
 			expectStoreMessage(txn, contactGroup.getId(), "foo",
 					fooPropertiesDict, 1, true, true);
 		}});

bramble-core/src/test/java/org/briarproject/bramble/record/RecordWriterImplTest.java

@@ -7,6 +7,7 @@ import org.junit.Test;
 
 import java.io.ByteArrayOutputStream;
 
+import static java.lang.System.arraycopy;
 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.test.TestUtils.getRandomBytes;
@@ -42,7 +43,7 @@ public class RecordWriterImplTest extends BrambleTestCase {
 		assertEquals(recordType, written[1]);
 		assertEquals(payloadLength, readUint16(written, 2));
 		byte[] writtenPayload = new byte[payloadLength];
-		System.arraycopy(written, RECORD_HEADER_BYTES, writtenPayload, 0,
+		arraycopy(written, RECORD_HEADER_BYTES, writtenPayload, 0,
 				payloadLength);
 		assertArrayEquals(payload, writtenPayload);
 	}

bramble-core/src/test/java/org/briarproject/bramble/sync/SyncIntegrationTest.java

@@ -27,11 +27,11 @@ import org.junit.Test;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.InputStream;
-import java.util.Arrays;
 import java.util.Collection;
 
 import javax.inject.Inject;
 
+import static java.util.Arrays.asList;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.PROTOCOL_VERSION;
 import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
@@ -90,7 +90,7 @@ public class SyncIntegrationTest extends BrambleTestCase {
 		byte[] body = "Hello world".getBytes("UTF-8");
 		message = messageFactory.createMessage(group.getId(), timestamp, body);
 		message1 = messageFactory.createMessage(group.getId(), timestamp, body);
-		messageIds = Arrays.asList(message.getId(), message1.getId());
+		messageIds = asList(message.getId(), message1.getId());
 	}
 
 	@Test

bramble-core/src/test/java/org/briarproject/bramble/system/UnixSecureRandomSpiTest.java

@@ -2,7 +2,6 @@ package org.briarproject.bramble.system;
 
 import org.briarproject.bramble.api.Bytes;
 import org.briarproject.bramble.test.BrambleTestCase;
-import org.briarproject.bramble.util.IoUtils;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -16,6 +15,7 @@ import java.util.Set;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
+import static org.briarproject.bramble.util.IoUtils.read;
 import static org.briarproject.bramble.util.OsUtils.isLinux;
 import static org.briarproject.bramble.util.OsUtils.isMac;
 import static org.junit.Assert.assertArrayEquals;
@@ -64,7 +64,7 @@ public class UnixSecureRandomSpiTest extends BrambleTestCase {
 		assertEquals(SEED_BYTES, urandom.length());
 		byte[] written = new byte[SEED_BYTES];
 		FileInputStream in = new FileInputStream(urandom);
-		IoUtils.read(in, written);
+		read(in, written);
 		in.close();
 		assertArrayEquals(seed, written);
 	}

bramble-core/src/test/java/org/briarproject/bramble/test/TestMessageFactory.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 
+import static java.lang.System.arraycopy;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 
 @NotNullByDefault
@@ -24,7 +25,7 @@ public class TestMessageFactory implements MessageFactory {
 	public byte[] getRawMessage(Message m) {
 		byte[] body = m.getBody();
 		byte[] raw = new byte[MESSAGE_HEADER_LENGTH + body.length];
-		System.arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
+		arraycopy(body, 0, raw, MESSAGE_HEADER_LENGTH, body.length);
 		return raw;
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/test/UTest.java

@@ -5,11 +5,11 @@ import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 import javax.annotation.Nonnull;
 
+import static java.util.Collections.sort;
 import static org.briarproject.bramble.test.UTest.Result.INCONCLUSIVE;
 import static org.briarproject.bramble.test.UTest.Result.LARGER;
 import static org.briarproject.bramble.test.UTest.Result.SMALLER;
@@ -80,7 +80,7 @@ public class UTest {
 		List<Value> sorted = new ArrayList<>(nA + nB);
 		for (Double d : a) sorted.add(new Value(d, true));
 		for (Double d : b) sorted.add(new Value(d, false));
-		Collections.sort(sorted);
+		sort(sorted);
 
 		// Assign ranks to the values
 		int i = 0, size = sorted.size();

bramble-core/src/test/java/org/briarproject/bramble/transport/ReorderingWindowTest.java

@@ -4,9 +4,9 @@ import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.transport.ReorderingWindow.Change;
 import org.junit.Test;
 
-import java.util.Arrays;
+import static java.util.Arrays.asList;
-import java.util.Collections;
+import static java.util.Collections.emptyList;
-
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.transport.TransportConstants.REORDERING_WINDOW_SIZE;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.junit.Assert.assertArrayEquals;
@@ -33,9 +33,9 @@ public class ReorderingWindowTest extends BrambleTestCase {
 		Change change = window.setSeen(0L);
 		// The window should slide by one element
 		assertEquals(1L, window.getBase());
-		assertEquals(Collections.singletonList((long) REORDERING_WINDOW_SIZE),
+		assertEquals(singletonList((long) REORDERING_WINDOW_SIZE),
 				change.getAdded());
-		assertEquals(Collections.singletonList(0L), change.getRemoved());
+		assertEquals(singletonList(0L), change.getRemoved());
 		// All elements in the window should be unseen
 		assertArrayEquals(bitmap, window.getBitmap());
 	}
@@ -48,8 +48,8 @@ public class ReorderingWindowTest extends BrambleTestCase {
 		Change change = window.setSeen(1L);
 		// The window should not slide
 		assertEquals(0L, window.getBase());
-		assertEquals(Collections.emptyList(), change.getAdded());
+		assertEquals(emptyList(), change.getAdded());
-		assertEquals(Collections.singletonList(1L), change.getRemoved());
+		assertEquals(singletonList(1L), change.getRemoved());
 		// The second element in the window should be seen
 		bitmap[0] = 0x40; // 0100 0000
 		assertArrayEquals(bitmap, window.getBitmap());
@@ -64,9 +64,9 @@ public class ReorderingWindowTest extends BrambleTestCase {
 		Change change = window.setSeen(aboveMidpoint);
 		// The window should slide by one element
 		assertEquals(1L, window.getBase());
-		assertEquals(Collections.singletonList((long) REORDERING_WINDOW_SIZE),
+		assertEquals(singletonList((long) REORDERING_WINDOW_SIZE),
 				change.getAdded());
-		assertEquals(Arrays.asList(0L, aboveMidpoint), change.getRemoved());
+		assertEquals(asList(0L, aboveMidpoint), change.getRemoved());
 		// The highest element below the midpoint should be seen
 		bitmap[bitmap.length / 2 - 1] = (byte) 0x01; // 0000 0001
 		assertArrayEquals(bitmap, window.getBitmap());
@@ -81,9 +81,9 @@ public class ReorderingWindowTest extends BrambleTestCase {
 		Change change = window.setSeen(0L);
 		// The window should slide by two elements
 		assertEquals(2L, window.getBase());
-		assertEquals(Arrays.asList((long) REORDERING_WINDOW_SIZE,
+		assertEquals(asList((long) REORDERING_WINDOW_SIZE,
 				(long) (REORDERING_WINDOW_SIZE + 1)), change.getAdded());
-		assertEquals(Collections.singletonList(0L), change.getRemoved());
+		assertEquals(singletonList(0L), change.getRemoved());
 		// All elements in the window should be unseen
 		assertArrayEquals(bitmap, window.getBitmap());
 	}
@@ -98,9 +98,9 @@ public class ReorderingWindowTest extends BrambleTestCase {
 		Change change = window.setSeen(aboveMidpoint);
 		// The window should slide by two elements
 		assertEquals(2L, window.getBase());
-		assertEquals(Arrays.asList((long) REORDERING_WINDOW_SIZE,
+		assertEquals(asList((long) REORDERING_WINDOW_SIZE,
 				(long) (REORDERING_WINDOW_SIZE + 1)), change.getAdded());
-		assertEquals(Arrays.asList(0L, aboveMidpoint), change.getRemoved());
+		assertEquals(asList(0L, aboveMidpoint), change.getRemoved());
 		// The second-highest element below the midpoint should be seen
 		bitmap[bitmap.length / 2 - 1] = (byte) 0x02; // 0000 0010
 		assertArrayEquals(bitmap, window.getBitmap());

bramble-core/src/test/java/org/briarproject/bramble/transport/TestStreamDecrypter.java

@@ -7,6 +7,7 @@ import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
 
+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.MAC_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_FRAME_LENGTH;
@@ -47,7 +48,7 @@ class TestStreamDecrypter implements StreamDecrypter {
 			if (read == -1) throw new EOFException();
 			offset += read;
 		}
-		System.arraycopy(frame, FRAME_HEADER_LENGTH, payload, 0, payloadLength);
+		arraycopy(frame, FRAME_HEADER_LENGTH, payload, 0, payloadLength);
 		return payloadLength;
 	}
 

bramble-java/src/main/java/org/briarproject/bramble/lifecycle/WindowsShutdownManagerImpl.java

@@ -16,7 +16,6 @@ import com.sun.jna.win32.W32APITypeMapper;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -26,6 +25,7 @@ import javax.annotation.concurrent.ThreadSafe;
 
 import static com.sun.jna.Library.OPTION_FUNCTION_MAPPER;
 import static com.sun.jna.Library.OPTION_TYPE_MAPPER;
+import static java.util.Collections.unmodifiableMap;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -51,7 +51,7 @@ class WindowsShutdownManagerImpl extends ShutdownManagerImpl {
 		Map<String, Object> m = new HashMap<>();
 		m.put(OPTION_TYPE_MAPPER, W32APITypeMapper.UNICODE);
 		m.put(OPTION_FUNCTION_MAPPER, W32APIFunctionMapper.UNICODE);
-		options = Collections.unmodifiableMap(m);
+		options = unmodifiableMap(m);
 	}
 
 	@Override

bramble-java/src/main/java/org/briarproject/bramble/plugin/modem/ModemImpl.java

@@ -26,6 +26,7 @@ import javax.annotation.Nullable;
 import jssc.SerialPortEvent;
 import jssc.SerialPortEventListener;
 
+import static java.lang.System.arraycopy;
 import static java.nio.charset.CodingErrorAction.IGNORE;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
@@ -375,7 +376,7 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
 					int off = i + 1;
 					if (off < b.length) {
 						byte[] data = new byte[b.length - off];
-						System.arraycopy(b, off, data, 0, data.length);
+						arraycopy(b, off, data, 0, data.length);
 						handleData(data);
 					}
 					return;

briar-android/src/main/java/org/briarproject/briar/android/ScreenFilterMonitorImpl.java

@@ -25,7 +25,6 @@ import java.security.cert.CertificateFactory;
 import java.security.cert.X509Certificate;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -46,6 +45,9 @@ import static android.content.pm.PackageInfo.REQUESTED_PERMISSION_GRANTED;
 import static android.content.pm.PackageManager.GET_PERMISSIONS;
 import static android.content.pm.PackageManager.GET_SIGNATURES;
 import static android.os.Build.VERSION.SDK_INT;
+import static java.util.Collections.emptySet;
+import static java.util.Collections.sort;
+import static java.util.Collections.unmodifiableList;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -105,8 +107,7 @@ class ScreenFilterMonitorImpl implements ScreenFilterMonitor, Service {
 	@UiThread
 	public Collection<AppDetails> getApps() {
 		if (cachedApps != null) return cachedApps;
-		Set<String> allowed = prefs.getStringSet(PREF_KEY_ALLOWED,
+		Set<String> allowed = prefs.getStringSet(PREF_KEY_ALLOWED, emptySet());
-				Collections.emptySet());
 		List<AppDetails> apps = new ArrayList<>();
 		List<PackageInfo> packageInfos =
 				pm.getInstalledPackages(GET_PERMISSIONS);
@@ -117,8 +118,8 @@ class ScreenFilterMonitorImpl implements ScreenFilterMonitor, Service {
 				apps.add(new AppDetails(name, packageInfo.packageName));
 			}
 		}
-		Collections.sort(apps, (a, b) -> a.name.compareTo(b.name));
+		sort(apps, (a, b) -> a.name.compareTo(b.name));
-		apps = Collections.unmodifiableList(apps);
+		apps = unmodifiableList(apps);
 		cachedApps = apps;
 		return apps;
 	}
@@ -127,8 +128,7 @@ class ScreenFilterMonitorImpl implements ScreenFilterMonitor, Service {
 	@UiThread
 	public void allowApps(Collection<String> packageNames) {
 		cachedApps = null;
-		Set<String> allowed = prefs.getStringSet(PREF_KEY_ALLOWED,
+		Set<String> allowed = prefs.getStringSet(PREF_KEY_ALLOWED, emptySet());
-				Collections.emptySet());
 		Set<String> merged = new HashSet<>(allowed);
 		merged.addAll(packageNames);
 		prefs.edit().putStringSet(PREF_KEY_ALLOWED, merged).apply();

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogCommentItem.java

@@ -4,10 +4,11 @@ import org.briarproject.briar.api.blog.BlogCommentHeader;
 import org.briarproject.briar.api.blog.BlogPostHeader;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
+import static java.util.Collections.sort;
+
 // This class is not thread-safe
 class BlogCommentItem extends BlogPostItem {
 
@@ -20,7 +21,7 @@ class BlogCommentItem extends BlogPostItem {
 	BlogCommentItem(BlogCommentHeader header) {
 		super(header, null);
 		postHeader = collectComments(header);
-		Collections.sort(comments, COMPARATOR);
+		sort(comments, COMPARATOR);
 	}
 
 	private BlogPostHeader collectComments(BlogPostHeader header) {

briar-android/src/main/java/org/briarproject/briar/android/reporting/BriarReportPrimer.java

@@ -7,7 +7,6 @@ import android.net.ConnectivityManager;
 import android.net.NetworkInfo;
 import android.net.wifi.WifiInfo;
 import android.net.wifi.WifiManager;
-import android.os.Build;
 import android.os.Environment;
 import android.os.Handler;
 import android.os.Looper;
@@ -23,7 +22,6 @@ import org.briarproject.briar.android.logging.BriefLogFormatter;
 import java.io.File;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.Callable;
@@ -41,6 +39,8 @@ import static android.content.Context.WIFI_SERVICE;
 import static android.net.ConnectivityManager.TYPE_MOBILE;
 import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.net.wifi.WifiManager.WIFI_STATE_ENABLED;
+import static android.os.Build.VERSION.SDK_INT;
+import static java.util.Collections.unmodifiableMap;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubInetAddress;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
@@ -90,7 +90,7 @@ public class BriarReportPrimer implements ReportPrimer {
 			ActivityManager.MemoryInfo mem = new ActivityManager.MemoryInfo();
 			am.getMemoryInfo(mem);
 			String systemMemory;
-			if (Build.VERSION.SDK_INT >= 16) {
+			if (SDK_INT >= 16) {
 				systemMemory = (mem.totalMem / 1024 / 1024) + " MiB total, "
 						+ (mem.availMem / 1024 / 1204) + " MiB free, "
 						+ (mem.threshold / 1024 / 1024) + " MiB threshold";
@@ -213,7 +213,7 @@ public class BriarReportPrimer implements ReportPrimer {
 					bt.getScanMode() == SCAN_MODE_CONNECTABLE_DISCOVERABLE;
 			// Is Bluetooth LE scanning and advertising supported?
 			boolean btLeApi = false, btLeScan = false, btLeAdvertise = false;
-			if (bt != null && Build.VERSION.SDK_INT >= 21) {
+			if (bt != null && SDK_INT >= 21) {
 				btLeApi = true;
 				btLeScan = bt.getBluetoothLeScanner() != null;
 				btLeAdvertise = bt.getBluetoothLeAdvertiser() != null;
@@ -255,7 +255,7 @@ public class BriarReportPrimer implements ReportPrimer {
 			// Git commit ID
 			customData.put("Commit ID", BuildConfig.GitHash);
 
-			return Collections.unmodifiableMap(customData);
+			return unmodifiableMap(customData);
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java

@@ -42,7 +42,6 @@ import org.briarproject.briar.android.Localizer;
 import org.briarproject.briar.android.navdrawer.NavDrawerActivity;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 import java.util.Locale;
 import java.util.logging.Logger;
@@ -67,6 +66,7 @@ import static android.provider.Settings.EXTRA_CHANNEL_ID;
 import static android.provider.Settings.System.DEFAULT_NOTIFICATION_URI;
 import static android.support.v4.view.ViewCompat.LAYOUT_DIRECTION_LTR;
 import static android.widget.Toast.LENGTH_SHORT;
+import static java.util.Arrays.asList;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -222,7 +222,7 @@ public class SettingsFragment extends PreferenceFragmentCompat
 		if (SDK_INT < 27) {
 			// remove System Default Theme option
 			List<CharSequence> entries =
-					new ArrayList<>(Arrays.asList(theme.getEntries()));
+					new ArrayList<>(asList(theme.getEntries()));
 			entries.remove(getString(R.string.pref_theme_system));
 			theme.setEntries(entries.toArray(new CharSequence[0]));
 		}

briar-android/src/main/java/org/briarproject/briar/android/splash/SplashScreenActivity.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.splash;
 
 import android.content.Intent;
-import android.os.Build;
 import android.os.Bundle;
 import android.os.Handler;
 import android.support.v7.preference.PreferenceManager;
@@ -21,6 +20,7 @@ import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
+import static android.os.Build.VERSION.SDK_INT;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.android.TestingConstants.EXPIRY_DATE;
 
@@ -40,7 +40,7 @@ public class SplashScreenActivity extends BaseActivity {
 	public void onCreate(Bundle state) {
 		super.onCreate(state);
 
-		if (Build.VERSION.SDK_INT >= 21) {
+		if (SDK_INT >= 21) {
 			getWindow().setExitTransition(new Fade());
 		}
 

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListControllerImpl.java

@@ -28,12 +28,12 @@ import org.briarproject.briar.api.client.PostHeader;
 import org.briarproject.briar.api.client.ThreadedMessage;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
+import static java.util.Collections.singletonList;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -186,7 +186,7 @@ public abstract class ThreadListControllerImpl<G extends NamedGroup, I extends T
 
 	@Override
 	public void markItemRead(I item) {
-		markItemsRead(Collections.singletonList(item));
+		markItemsRead(singletonList(item));
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/view/KeyboardAwareLinearLayout.java

@@ -8,7 +8,6 @@ import android.annotation.TargetApi;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.graphics.Rect;
-import android.os.Build;
 import android.preference.PreferenceManager;
 import android.support.annotation.UiThread;
 import android.util.AttributeSet;
@@ -26,6 +25,7 @@ import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 import static android.content.Context.WINDOW_SERVICE;
+import static android.os.Build.VERSION.SDK_INT;
 import static android.view.Surface.ROTATION_270;
 import static android.view.Surface.ROTATION_90;
 import static java.util.Objects.requireNonNull;
@@ -106,7 +106,7 @@ public class KeyboardAwareLinearLayout extends LinearLayout {
 			return;
 		}
 
-		if (viewInset == 0 && Build.VERSION.SDK_INT >= 21)
+		if (viewInset == 0 && SDK_INT >= 21)
 			viewInset = getViewInset();
 		int availableHeight =
 				getRootView().getHeight() - statusBarHeight - viewInset;

briar-android/src/test/java/org/briarproject/briar/android/forum/ForumActivityTest.java

@@ -21,8 +21,7 @@ import org.robolectric.Robolectric;
 import org.robolectric.RobolectricTestRunner;
 import org.robolectric.annotation.Config;
 
-import java.util.Arrays;
+import static java.util.Arrays.asList;
-
 import static junit.framework.Assert.assertEquals;
 import static junit.framework.Assert.assertTrue;
 import static org.briarproject.bramble.api.identity.AuthorInfo.Status.UNKNOWN;
@@ -91,7 +90,7 @@ public class ForumActivityTest {
 			forumItems[i].setLevel(LEVELS[i]);
 		}
 		ThreadItemList<ForumItem> list = new ThreadItemListImpl<>();
-		list.addAll(Arrays.asList(forumItems));
+		list.addAll(asList(forumItems));
 		return list;
 	}
 

briar-core/src/main/java/org/briarproject/briar/blog/BlogManagerImpl.java

@@ -38,7 +38,6 @@ import java.security.GeneralSecurityException;
 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.List;
@@ -50,6 +49,7 @@ import java.util.concurrent.CopyOnWriteArrayList;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
+import static java.util.Collections.emptyMap;
 import static org.briarproject.bramble.api.identity.AuthorInfo.Status.NONE;
 import static org.briarproject.briar.api.blog.BlogConstants.KEY_AUTHOR;
 import static org.briarproject.briar.api.blog.BlogConstants.KEY_COMMENT;
@@ -560,8 +560,7 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 	private BlogPostHeader getPostHeaderFromMetadata(Transaction txn,
 			GroupId groupId, MessageId id, BdfDictionary meta)
 			throws DbException, FormatException {
-		return getPostHeaderFromMetadata(txn, groupId, id, meta,
+		return getPostHeaderFromMetadata(txn, groupId, id, meta, emptyMap());
-				Collections.emptyMap());
 	}
 
 	private BlogPostHeader getPostHeaderFromMetadata(Transaction txn,

briar-core/src/main/java/org/briarproject/briar/client/MessageTreeImpl.java

@@ -6,7 +6,6 @@ import org.briarproject.briar.api.client.MessageTree;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
@@ -14,6 +13,9 @@ import java.util.Map;
 
 import javax.annotation.concurrent.ThreadSafe;
 
+import static java.util.Collections.singletonList;
+import static java.util.Collections.sort;
+
 @ThreadSafe
 @NotNullByDefault
 public class MessageTreeImpl<T extends MessageTree.MessageNode>
@@ -47,7 +49,7 @@ public class MessageTreeImpl<T extends MessageTree.MessageNode>
 
 	@Override
 	public synchronized void add(T node) {
-		add(Collections.singletonList(node));
+		add(singletonList(node));
 	}
 
 	private void markAsUnsorted(List<T> list) {
@@ -69,7 +71,7 @@ public class MessageTreeImpl<T extends MessageTree.MessageNode>
 
 	private void sortUnsorted() {
 		for (List<T> list : unsortedLists) {
-			Collections.sort(list, comparator);
+			sort(list, comparator);
 		}
 		unsortedLists.clear();
 	}
@@ -87,9 +89,9 @@ public class MessageTreeImpl<T extends MessageTree.MessageNode>
 	public synchronized void setComparator(Comparator<T> comparator) {
 		this.comparator = comparator;
 		// Sort all lists with the new comparator
-		Collections.sort(roots, comparator);
+		sort(roots, comparator);
 		for (Map.Entry<MessageId, List<T>> entry : nodeMap.entrySet()) {
-			Collections.sort(entry.getValue(), comparator);
+			sort(entry.getValue(), comparator);
 		}
 	}
 

briar-core/src/main/java/org/briarproject/briar/feed/NoDns.java

@@ -2,13 +2,14 @@ package org.briarproject.briar.feed;
 
 import java.net.InetAddress;
 import java.net.UnknownHostException;
-import java.util.Collections;
 import java.util.List;
 
 import javax.inject.Inject;
 
 import okhttp3.Dns;
 
+import static java.util.Collections.singletonList;
+
 class NoDns implements Dns {
 
 	private static final byte[] UNSPECIFIED_ADDRESS = new byte[4];
@@ -22,7 +23,7 @@ class NoDns implements Dns {
 			throws UnknownHostException {
 		InetAddress unspecified =
 				InetAddress.getByAddress(hostname, UNSPECIFIED_ADDRESS);
-		return Collections.singletonList(unspecified);
+		return singletonList(unspecified);
 	}
 
 }

briar-core/src/main/java/org/briarproject/briar/forum/ForumManagerImpl.java

@@ -32,7 +32,6 @@ import org.briarproject.briar.api.forum.event.ForumPostReceivedEvent;
 import java.security.GeneralSecurityException;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -45,6 +44,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
+import static java.util.Collections.emptyMap;
 import static org.briarproject.bramble.api.identity.AuthorInfo.Status.OURSELVES;
 import static org.briarproject.briar.api.forum.ForumConstants.KEY_AUTHOR;
 import static org.briarproject.briar.api.forum.ForumConstants.KEY_LOCAL;
@@ -249,7 +249,7 @@ class ForumManagerImpl extends BdfIncomingMessageHook implements ForumManager {
 
 	private ForumPostHeader getForumPostHeader(Transaction txn, MessageId id,
 			BdfDictionary meta) throws DbException, FormatException {
-		return getForumPostHeader(txn, id, meta, Collections.emptyMap());
+		return getForumPostHeader(txn, id, meta, emptyMap());
 	}
 
 	private ForumPostHeader getForumPostHeader(Transaction txn, MessageId id,

briar-core/src/main/java/org/briarproject/briar/introduction/IntroductionValidator.java

@@ -15,10 +15,9 @@ import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.api.client.SessionId;
 
-import java.util.Collections;
-
 import javax.annotation.concurrent.Immutable;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.crypto.CryptoConstants.MAC_BYTES;
 import static org.briarproject.bramble.api.crypto.CryptoConstants.MAX_SIGNATURE_BYTES;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
@@ -84,8 +83,7 @@ class IntroductionValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 
@@ -118,8 +116,7 @@ class IntroductionValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 
@@ -144,8 +141,7 @@ class IntroductionValidator extends BdfMessageValidator {
 				.encodeMetadata(AUTH, sessionId, m.getTimestamp(), false, false,
 						false);
 		MessageId dependency = new MessageId(previousMessageId);
-		return new BdfMessageContext(meta,
+		return new BdfMessageContext(meta, singletonList(dependency));
-				Collections.singletonList(dependency));
 	}
 
 	private BdfMessageContext validateActivateMessage(Message m, BdfList body)
@@ -169,8 +165,7 @@ class IntroductionValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 
@@ -192,8 +187,7 @@ class IntroductionValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 

briar-core/src/main/java/org/briarproject/briar/privategroup/PrivateGroupManagerImpl.java

@@ -42,7 +42,6 @@ import org.briarproject.briar.api.privategroup.event.GroupMessageAddedEvent;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -54,6 +53,7 @@ import java.util.concurrent.CopyOnWriteArrayList;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
+import static java.util.Collections.emptyMap;
 import static org.briarproject.bramble.api.identity.AuthorInfo.Status.OURSELVES;
 import static org.briarproject.bramble.api.identity.AuthorInfo.Status.UNVERIFIED;
 import static org.briarproject.bramble.api.identity.AuthorInfo.Status.VERIFIED;
@@ -574,7 +574,7 @@ class PrivateGroupManagerImpl extends BdfIncomingMessageHook
 			BdfDictionary meta, boolean local)
 			throws DbException, FormatException {
 		GroupMessageHeader header = getGroupMessageHeader(txn, m.getGroupId(),
-				m.getId(), meta, Collections.emptyMap());
+				m.getId(), meta, emptyMap());
 		String text = getMessageText(clientHelper.toList(m));
 		txn.attach(new GroupMessageAddedEvent(m.getGroupId(), header, text,
 				local));
@@ -584,7 +584,7 @@ class PrivateGroupManagerImpl extends BdfIncomingMessageHook
 			BdfDictionary meta, boolean local, Visibility v)
 			throws DbException, FormatException {
 		JoinMessageHeader header = getJoinMessageHeader(txn, m.getGroupId(),
-				m.getId(), meta, Collections.emptyMap(), v);
+				m.getId(), meta, emptyMap(), v);
 		txn.attach(new GroupMessageAddedEvent(m.getGroupId(), header, "",
 				local));
 	}

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/GroupInvitationValidator.java

@@ -19,10 +19,10 @@ import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
 
 import java.security.GeneralSecurityException;
-import java.util.Collections;
 
 import javax.annotation.concurrent.Immutable;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
 import static org.briarproject.bramble.util.ValidationUtils.checkLength;
 import static org.briarproject.bramble.util.ValidationUtils.checkSize;
@@ -120,8 +120,7 @@ class GroupInvitationValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 
@@ -139,8 +138,7 @@ class GroupInvitationValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 

briar-core/src/main/java/org/briarproject/briar/sharing/SharingValidator.java

@@ -15,10 +15,9 @@ import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
 
-import java.util.Collections;
-
 import javax.annotation.concurrent.Immutable;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.util.ValidationUtils.checkLength;
 import static org.briarproject.bramble.util.ValidationUtils.checkSize;
 import static org.briarproject.briar.api.sharing.SharingConstants.MAX_INVITATION_TEXT_LENGTH;
@@ -70,8 +69,7 @@ abstract class SharingValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 
@@ -93,8 +91,7 @@ abstract class SharingValidator extends BdfMessageValidator {
 			return new BdfMessageContext(meta);
 		} else {
 			MessageId dependency = new MessageId(previousMessageId);
-			return new BdfMessageContext(meta,
+			return new BdfMessageContext(meta, singletonList(dependency));
-					Collections.singletonList(dependency));
 		}
 	}
 

briar-core/src/test/java/org/briarproject/briar/client/MessageTreeImplTest.java

@@ -5,11 +5,11 @@ import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.MessageTree;
 import org.junit.Test;
 
-import java.util.Arrays;
-import java.util.Collections;
-
 import javax.annotation.Nullable;
 
+import static java.util.Arrays.asList;
+import static java.util.Arrays.copyOf;
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.junit.Assert.assertEquals;
 
@@ -48,8 +48,8 @@ public class MessageTreeImplTest {
 		nodes[3].setTimestamp(timestamp - 2);
 		nodes[2].setTimestamp(timestamp - 1);
 		// add all nodes except the last one
-		tree.add(Arrays.asList(Arrays.copyOf(nodes, nodes.length - 1)));
+		tree.add(asList(copyOf(nodes, nodes.length - 1)));
-		tree.add(Collections.singletonList(nodes[nodes.length - 1]));
+		tree.add(singletonList(nodes[nodes.length - 1]));
 		TestNode[] sortedNodes =
 				tree.depthFirstOrder().toArray(new TestNode[5]);
 		assertEquals(nodes[4], sortedNodes[0]);

briar-core/src/test/java/org/briarproject/briar/privategroup/GroupMessageValidatorTest.java

@@ -16,10 +16,11 @@ import org.jmock.Expectations;
 import org.junit.Test;
 
 import java.security.GeneralSecurityException;
-import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
@@ -178,7 +179,7 @@ public class GroupMessageValidatorTest extends ValidatorTestCase {
 		BdfMessageContext messageContext =
 				validator.validateMessage(message, group, body);
 		assertExpectedMessageContext(messageContext, JOIN, creatorList,
-				Collections.emptyList());
+				emptyList());
 		assertTrue(messageContext.getDictionary()
 				.getBoolean(KEY_INITIAL_JOIN_MSG));
 	}
@@ -363,7 +364,7 @@ public class GroupMessageValidatorTest extends ValidatorTestCase {
 		BdfMessageContext messageContext =
 				validator.validateMessage(message, group, body);
 		assertExpectedMessageContext(messageContext, JOIN, memberList,
-				Collections.emptyList());
+				emptyList());
 		assertFalse(messageContext.getDictionary()
 				.getBoolean(KEY_INITIAL_JOIN_MSG));
 	}
@@ -606,7 +607,7 @@ public class GroupMessageValidatorTest extends ValidatorTestCase {
 		BdfMessageContext messageContext =
 				validator.validateMessage(message, group, body);
 		assertExpectedMessageContext(messageContext, POST, memberList,
-				Arrays.asList(parentId, previousMsgId));
+				asList(parentId, previousMsgId));
 		assertArrayEquals(previousMsgId.getBytes(),
 				messageContext.getDictionary().getRaw(KEY_PREVIOUS_MSG_ID));
 		assertArrayEquals(parentId.getBytes(),
@@ -621,7 +622,7 @@ public class GroupMessageValidatorTest extends ValidatorTestCase {
 		BdfMessageContext messageContext =
 				validator.validateMessage(message, group, body);
 		assertExpectedMessageContext(messageContext, POST, memberList,
-				Collections.singletonList(previousMsgId));
+				singletonList(previousMsgId));
 		assertArrayEquals(previousMsgId.getBytes(),
 				messageContext.getDictionary().getRaw(KEY_PREVIOUS_MSG_ID));
 		assertFalse(

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/GroupInvitationManagerImplTest.java

@@ -35,14 +35,16 @@ import org.jmock.Expectations;
 import org.jmock.lib.legacy.ClassImposteriser;
 import org.junit.Test;
 
-import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
 import javax.annotation.Nullable;
 
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyMap;
+import static java.util.Collections.singletonList;
+import static java.util.Collections.singletonMap;
 import static junit.framework.TestCase.fail;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
@@ -112,9 +114,8 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 	private final BdfDictionary bdfSession =
 			BdfDictionary.of(new BdfEntry("f", "o"));
 	private final Map<MessageId, BdfDictionary> oneResult =
-			Collections.singletonMap(storageMessage.getId(), bdfSession);
+			singletonMap(storageMessage.getId(), bdfSession);
-	private final Map<MessageId, BdfDictionary> noResults =
+	private final Map<MessageId, BdfDictionary> noResults = emptyMap();
-			Collections.emptyMap();
 
 
 	public GroupInvitationManagerImplTest() {
@@ -156,7 +157,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(false));
 			oneOf(db).addGroup(txn, localGroup);
 			oneOf(db).getContacts(txn);
-			will(returnValue(Collections.singletonList(contact)));
+			will(returnValue(singletonList(contact)));
 		}});
 		expectAddingContact(contact);
 		groupInvitationManager.createLocalState(txn);
@@ -192,7 +193,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 					.mergeGroupMetadata(txn, contactGroup.getId(), meta);
 			oneOf(db).getGroups(txn, PrivateGroupManager.CLIENT_ID,
 					PrivateGroupManager.MAJOR_VERSION);
-			will(returnValue(Collections.singletonList(privateGroup)));
+			will(returnValue(singletonList(privateGroup)));
 			oneOf(privateGroupManager).isMember(txn, privateGroup.getId(),
 					c.getAuthor());
 			will(returnValue(true));
@@ -743,7 +744,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).startTransaction(true);
 			will(returnValue(txn));
 			oneOf(db).getContacts(txn);
-			will(returnValue(Collections.singletonList(contact)));
+			will(returnValue(singletonList(contact)));
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
 					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
@@ -836,7 +837,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 		expectAddingMember(privateGroup.getId(), contact);
 		context.checking(new Expectations() {{
 			oneOf(db).getContactsByAuthorId(txn, author.getId());
-			will(returnValue(Collections.singletonList(contact)));
+			will(returnValue(singletonList(contact)));
 		}});
 		groupInvitationManager.addingMember(txn, privateGroup.getId(), author);
 	}
@@ -847,8 +848,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 				author.getId(), getRandomString(5), true, true);
 		Contact contact3 = new Contact(new ContactId(3), author,
 				author.getId(), getRandomString(5), true, true);
-		Collection<Contact> contacts =
+		Collection<Contact> contacts = asList(contact, contact2, contact3);
-				Arrays.asList(contact, contact2, contact3);
 
 		Group contactGroup2 = getGroup(CLIENT_ID, MAJOR_VERSION);
 		Group contactGroup3 = getGroup(CLIENT_ID, MAJOR_VERSION);
@@ -861,9 +861,9 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 				BdfDictionary.of(new BdfEntry("f3", "o"));
 
 		expectGetSession(oneResult, sessionId, contactGroup.getId());
-		expectGetSession(Collections.singletonMap(storageId2, bdfSession2),
+		expectGetSession(singletonMap(storageId2, bdfSession2),
 				sessionId, contactGroup2.getId());
-		expectGetSession(Collections.singletonMap(storageId3, bdfSession3),
+		expectGetSession(singletonMap(storageId3, bdfSession3),
 				sessionId, contactGroup3.getId());
 
 		context.checking(new Expectations() {{

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/InviteeProtocolEngineTest.java

@@ -11,9 +11,9 @@ import org.briarproject.briar.api.privategroup.GroupMessage;
 import org.jmock.Expectations;
 import org.junit.Test;
 
-import java.util.Collections;
 import java.util.Map;
 
+import static java.util.Collections.singletonMap;
 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.Group.Visibility.VISIBLE;
@@ -753,7 +753,7 @@ public class InviteeProtocolEngineTest extends AbstractProtocolEngineTest {
 		BdfDictionary query = BdfDictionary.of(new BdfEntry("query", ""));
 		BdfDictionary meta = BdfDictionary.of(new BdfEntry("meta", ""));
 		Map<MessageId, BdfDictionary> invites =
-				Collections.singletonMap(lastRemoteMessageId, meta);
+				singletonMap(lastRemoteMessageId, meta);
 		context.checking(new Expectations() {{
 			oneOf(messageParser)
 					.getInvitesAvailableToAnswerQuery(privateGroupId);

briar-core/src/test/java/org/briarproject/briar/sharing/BlogSharingManagerImplTest.java

@@ -28,10 +28,11 @@ import org.jmock.Expectations;
 import org.junit.Test;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
+import static java.util.Collections.emptyMap;
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
 import static org.briarproject.bramble.test.TestUtils.getGroup;
@@ -66,8 +67,7 @@ public class BlogSharingManagerImplTest extends BrambleMockTestCase {
 	private final Contact contact =
 			new Contact(contactId, author, localAuthor.getId(),
 					getRandomString(5), true, true);
-	private final Collection<Contact> contacts =
+	private final Collection<Contact> contacts = singletonList(contact);
-			Collections.singletonList(contact);
 	private final Group localGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 	private final Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 	private final Group blogGroup =
@@ -120,7 +120,7 @@ public class BlogSharingManagerImplTest extends BrambleMockTestCase {
 	private void expectAddingContact(Transaction txn) throws Exception {
 		BdfDictionary meta = BdfDictionary.of(
 				new BdfEntry(GROUP_KEY_CONTACT_ID, contactId.getInt()));
-		Map<MessageId, BdfDictionary> sessions = Collections.emptyMap();
+		Map<MessageId, BdfDictionary> sessions = emptyMap();
 
 		context.checking(new Expectations() {{
 			// Create the contact group and share it with the contact

briar-headless/src/main/java/org/briarproject/briar/headless/Router.kt

@@ -16,6 +16,7 @@ import org.briarproject.briar.headless.contact.ContactController
 import org.briarproject.briar.headless.event.WebSocketController
 import org.briarproject.briar.headless.forums.ForumController
 import org.briarproject.briar.headless.messaging.MessagingController
+import java.lang.Integer.parseInt
 import java.lang.Runtime.getRuntime
 import java.lang.System.exit
 import java.util.concurrent.atomic.AtomicBoolean
@@ -128,7 +129,7 @@ constructor(
 fun Context.getContactIdFromPathParam(): ContactId {
     val contactString = pathParam("contactId")
     val contactInt = try {
-        Integer.parseInt(contactString)
+        parseInt(contactString)
     } catch (e: NumberFormatException) {
         throw NotFoundResponse()
     }