Miscellaneous code cleanups.

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

@@ -13,8 +13,7 @@ import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.network.NetworkStatus;
 import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.system.Scheduler;
 
 import java.util.concurrent.Future;
@@ -34,13 +33,13 @@ import static android.net.ConnectivityManager.CONNECTIVITY_ACTION;
 import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.os.PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED;
+import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
 
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 class AndroidNetworkManager implements NetworkManager, Service {
 
 	private static final Logger LOG =
@@ -57,6 +56,7 @@ class AndroidNetworkManager implements NetworkManager, Service {
 			new AtomicReference<>();
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
+	@Nullable
 	private volatile BroadcastReceiver networkStateReceiver = null;
 
 	@Inject
@@ -90,9 +90,8 @@ class AndroidNetworkManager implements NetworkManager, Service {
 
 	@Override
 	public NetworkStatus getNetworkStatus() {
-		ConnectivityManager cm = (ConnectivityManager)
+		ConnectivityManager cm = (ConnectivityManager) requireNonNull(
-				appContext.getSystemService(CONNECTIVITY_SERVICE);
+				appContext.getSystemService(CONNECTIVITY_SERVICE));
-		if (cm == null) throw new AssertionError();
 		NetworkInfo net = cm.getActiveNetworkInfo();
 		boolean connected = net != null && net.isConnected();
 		boolean wifi = connected && net.getType() == TYPE_WIFI;

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

@@ -32,6 +32,7 @@ import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.os.Build.VERSION.SDK_INT;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Logger.getLogger;
 
 @NotNullByDefault
@@ -67,10 +68,8 @@ class AndroidLanTcpPlugin extends LanTcpPlugin implements EventListener {
 		// Don't execute more than one connection status check at a time
 		connectionStatusExecutor =
 				new PoliteExecutor("AndroidLanTcpPlugin", ioExecutor, 1);
-		ConnectivityManager connectivityManager = (ConnectivityManager)
+		connectivityManager = (ConnectivityManager) requireNonNull(
-				appContext.getSystemService(CONNECTIVITY_SERVICE);
+				appContext.getSystemService(CONNECTIVITY_SERVICE));
-		if (connectivityManager == null) throw new AssertionError();
-		this.connectivityManager = connectivityManager;
 		wifiManager = (WifiManager) appContext.getApplicationContext()
 				.getSystemService(WIFI_SERVICE);
 		socketFactory = SocketFactory.getDefault();

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

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

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

@@ -60,14 +60,14 @@ class AndroidLocationUtils implements LocationUtils {
 	}
 
 	private String getCountryFromPhoneNetwork() {
-		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
+		TelephonyManager tm = (TelephonyManager)
-		TelephonyManager tm = (TelephonyManager) o;
+				appContext.getSystemService(TELEPHONY_SERVICE);
-		return tm.getNetworkCountryIso();
+		return tm == null ? "" : tm.getNetworkCountryIso();
 	}
 
 	private String getCountryFromSimCard() {
-		Object o = appContext.getSystemService(TELEPHONY_SERVICE);
+		TelephonyManager tm = (TelephonyManager)
-		TelephonyManager tm = (TelephonyManager) o;
+				appContext.getSystemService(TELEPHONY_SERVICE);
-		return tm.getSimCountryIso();
+		return tm == null ? "" : tm.getSimCountryIso();
 	}
 }

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

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

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

@@ -33,6 +33,7 @@ public class BdfList extends ArrayList<Object> {
 		super(items);
 	}
 
+	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	private boolean isInRange(int index) {
 		return index >= 0 && index < size();
 	}

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

@@ -11,7 +11,7 @@ public class TransportId {
 	/**
 	 * The maximum length of a transport identifier in UTF-8 bytes.
 	 */
-	public static int MAX_TRANSPORT_ID_LENGTH = 100;
+	public static final int MAX_TRANSPORT_ID_LENGTH = 100;
 
 	private final String id;
 

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

@@ -17,7 +17,7 @@ public class ClientId implements Comparable<ClientId> {
 	/**
 	 * The maximum length of a client identifier in UTF-8 bytes.
 	 */
-	public static int MAX_CLIENT_ID_LENGTH = 100;
+	public static final int MAX_CLIENT_ID_LENGTH = 100;
 
 	private final String id;
 

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

@@ -68,7 +68,7 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testKeySetIteratorIsOrderedByKeys() throws Exception {
+	public void testKeySetIteratorIsOrderedByKeys() {
 		BdfDictionary d = new BdfDictionary();
 		d.put("a", 1);
 		d.put("d", 4);
@@ -87,7 +87,7 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testValuesIteratorIsOrderedByKeys() throws Exception {
+	public void testValuesIteratorIsOrderedByKeys() {
 		BdfDictionary d = new BdfDictionary();
 		d.put("a", 1);
 		d.put("d", 4);
@@ -106,7 +106,7 @@ public class BdfDictionaryTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testEntrySetIteratorIsOrderedByKeys() throws Exception {
+	public void testEntrySetIteratorIsOrderedByKeys() {
 		BdfDictionary d = new BdfDictionary();
 		d.put("a", 1);
 		d.put("d", 4);

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

@@ -6,8 +6,7 @@ import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 
 import java.io.BufferedReader;
 import java.io.File;
@@ -27,8 +26,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.fromHexString;
 import static org.briarproject.bramble.util.StringUtils.toHexString;
 
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 class AccountManagerImpl implements AccountManager {
 
 	private static final Logger LOG =
@@ -104,7 +102,7 @@ class AccountManagerImpl implements AccountManager {
 	}
 
 	// Locking: stateChangeLock
-	protected boolean storeEncryptedDatabaseKey(String hex) {
+	boolean storeEncryptedDatabaseKey(String hex) {
 		LOG.info("Storing database key in file");
 		// Create the directory if necessary
 		if (databaseConfig.getDatabaseKeyDirectory().mkdirs())

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

@@ -191,6 +191,7 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 			streamWriter.sendEndOfStream();
 			// Skip any remaining records from the incoming stream
 			try {
+				//noinspection InfiniteLoopStatement
 				while (true) recordReader.readRecord();
 			} catch (EOFException expected) {
 				LOG.info("End of stream");

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

@@ -15,7 +15,7 @@ class AsciiArmour {
 		int length = wrapped.length();
 		for (int i = 0; i < length; i += lineLength) {
 			int end = Math.min(i + lineLength, length);
-			s.append(wrapped.substring(i, end));
+			s.append(wrapped, i, end);
 			s.append("\r\n");
 		}
 		return s.toString();

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

@@ -159,6 +159,7 @@ public class MessageEncrypter {
 			printUsage();
 			System.exit(1);
 		}
+		//noinspection IfCanBeSwitch
 		if (args[0].equals("generate")) {
 			if (args.length != 3) {
 				printUsage();

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

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

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

@@ -339,6 +339,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		this.clock = clock;
 	}
 
+	@SuppressWarnings("unused")
 	protected void open(String driverClass, boolean reopen, SecretKey key,
 			@Nullable MigrationListener listener) throws DbException {
 		// Load the JDBC driver
@@ -768,7 +769,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			for (Entry<ContactId, Boolean> e : visibility.entrySet()) {
 				ContactId c = e.getKey();
 				boolean offered = removeOfferedMessage(txn, c, m.getId());
-				boolean seen = offered || (sender != null && c.equals(sender));
+				boolean seen = offered || c.equals(sender);
 				addStatus(txn, m.getId(), c, m.getGroupId(), m.getTimestamp(),
 						raw.length, state, e.getValue(), messageShared,
 						false, seen);

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

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

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

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

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

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

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

@@ -80,6 +80,7 @@ class LanTcpPlugin extends TcpPlugin {
 				locals.add(new InetSocketAddress(local, 0));
 			}
 		}
+		//noinspection Java8ListSort
 		sort(locals, ADDRESS_COMPARATOR);
 		return locals;
 	}

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

@@ -85,6 +85,7 @@ abstract class TcpPlugin implements DuplexPlugin {
 	/**
 	 * Returns true if connections to the given address can be attempted.
 	 */
+	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	protected abstract boolean isConnectable(InetSocketAddress remote);
 
 	TcpPlugin(Executor ioExecutor, Backoff backoff,

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

@@ -13,7 +13,7 @@ abstract class Frame {
 
 	static final byte ACK_FLAG = (byte) 128, FIN_FLAG = 64;
 
-	protected final byte[] buf;
+	final byte[] buf;
 
 	Frame(byte[] buf) {
 		this.buf = buf;

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

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

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

@@ -52,6 +52,7 @@ class ReceiverInputStream extends InputStream {
 		return len;
 	}
 
+	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	private boolean receive() throws IOException {
 		if (length != 0) throw new AssertionError();
 		if (data != null && data.isLastFrame()) {

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

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

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

@@ -44,6 +44,7 @@ public class DevReportServer {
 		TokenBucket bucket = new TokenBucket();
 		bucket.start();
 		try {
+			//noinspection InfiniteLoopStatement
 			while (true) {
 				Socket s = ss.accept();
 				System.out.println("Incoming connection");
@@ -103,6 +104,7 @@ public class DevReportServer {
 		@Override
 		public void run() {
 			try {
+				//noinspection InfiniteLoopStatement
 				while (true) {
 					// If the bucket isn't full, add a token
 					if (semaphore.availablePermits() < MAX_TOKENS) {
@@ -134,6 +136,8 @@ public class DevReportServer {
 			try {
 				socket.setSoTimeout(SOCKET_TIMEOUT_MS);
 				in = getInputStream(socket);
+				// Directory may already exist
+				//noinspection ResultOfMethodCallIgnored
 				reportDir.mkdirs();
 				reportFile = createTempFile(FILE_PREFIX, FILE_SUFFIX,
 						reportDir);
@@ -153,7 +157,8 @@ public class DevReportServer {
 				System.out.println("Saved " + length + " bytes");
 			} catch (IOException e) {
 				e.printStackTrace();
-				if (reportFile != null) reportFile.delete();
+				if (reportFile != null && !reportFile.delete())
+					System.err.println("Failed to delete report");
 			} finally {
 				tryToClose(in);
 				tryToClose(out);

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

@@ -111,17 +111,15 @@ class DevReporterImpl implements DevReporter, EventListener {
 		LOG.info("Sending reports to developers");
 		for (File f : reports) {
 			OutputStream out = null;
-			InputStream in = null;
 			try {
 				Socket s = connectToDevelopers();
 				out = getOutputStream(s);
-				in = new FileInputStream(f);
+				InputStream in = new FileInputStream(f);
 				copyAndClose(in, out);
-				f.delete();
+				if (!f.delete()) LOG.warning("Failed to delete report");
 			} catch (IOException e) {
 				LOG.log(WARNING, "Failed to send reports", e);
 				tryToClose(out, LOG, WARNING);
-				tryToClose(in, LOG, WARNING);
 				return;
 			}
 		}

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

@@ -28,6 +28,7 @@ class SocksSocket extends Socket {
 			"Address type not supported"
 	};
 
+	@SuppressWarnings("MismatchedReadAndWriteOfArray")
 	private static final byte[] UNSPECIFIED_ADDRESS = new byte[4];
 
 	private final SocketAddress proxy;

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

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

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

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

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

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

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

@@ -23,7 +23,7 @@ import static org.junit.Assert.assertEquals;
 public class EllipticCurveMultiplicationTest extends BrambleTestCase {
 
 	@Test
-	public void testMultiplierProducesSameResultsAsDefault() throws Exception {
+	public void testMultiplierProducesSameResultsAsDefault() {
 		// Instantiate the default implementation of the curve
 		X9ECParameters defaultX9Parameters =
 				TeleTrusTNamedCurves.getByName("brainpoolp256r1");

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

@@ -64,7 +64,7 @@ public class KeyAgreementTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testRfc7748TestVector() throws Exception {
+	public void testRfc7748TestVector() {
 		// Private keys need to be clamped because curve25519-java does the
 		// clamping at key generation time, not multiplication time
 		byte[] aPriv = Curve25519KeyParser.clamp(fromHexString(ALICE_PRIVATE));

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

@@ -23,7 +23,7 @@ public class KeyEncodingAndParsingTest extends BrambleTestCase {
 			new CryptoComponentImpl(new TestSecureRandomProvider(), null);
 
 	@Test
-	public void testAgreementPublicKeyLength() throws Exception {
+	public void testAgreementPublicKeyLength() {
 		// Generate 10 agreement key pairs
 		for (int i = 0; i < 10; i++) {
 			KeyPair keyPair = crypto.generateAgreementKeyPair();
@@ -70,7 +70,7 @@ public class KeyEncodingAndParsingTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testAgreementKeyParserByFuzzing() throws Exception {
+	public void testAgreementKeyParserByFuzzing() {
 		KeyParser parser = crypto.getAgreementKeyParser();
 		// Generate a key pair to get the proper public key length
 		KeyPair p = crypto.generateAgreementKeyPair();
@@ -92,7 +92,7 @@ public class KeyEncodingAndParsingTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testSignaturePublicKeyLength() throws Exception {
+	public void testSignaturePublicKeyLength() {
 		// Generate 10 signature key pairs
 		for (int i = 0; i < 10; i++) {
 			KeyPair keyPair = crypto.generateSignatureKeyPair();
@@ -159,7 +159,7 @@ public class KeyEncodingAndParsingTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testSignatureKeyParserByFuzzing() throws Exception {
+	public void testSignatureKeyParserByFuzzing() {
 		KeyParser parser = crypto.getSignatureKeyParser();
 		// Generate a key pair to get the proper public key length
 		KeyPair p = crypto.generateSignatureKeyPair();

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

@@ -19,7 +19,7 @@ import static org.junit.Assert.assertEquals;
 public class ScryptKdfTest extends BrambleTestCase {
 
 	@Test
-	public void testPasswordAffectsKey() throws Exception {
+	public void testPasswordAffectsKey() {
 		PasswordBasedKdf kdf = new ScryptKdf(new SystemClock());
 		byte[] salt = getRandomBytes(32);
 		Set<Bytes> keys = new HashSet<>();
@@ -31,7 +31,7 @@ public class ScryptKdfTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testSaltAffectsKey() throws Exception {
+	public void testSaltAffectsKey() {
 		PasswordBasedKdf kdf = new ScryptKdf(new SystemClock());
 		String password = getRandomString(16);
 		Set<Bytes> keys = new HashSet<>();
@@ -43,7 +43,7 @@ public class ScryptKdfTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testCostParameterAffectsKey() throws Exception {
+	public void testCostParameterAffectsKey() {
 		PasswordBasedKdf kdf = new ScryptKdf(new SystemClock());
 		String password = getRandomString(16);
 		byte[] salt = getRandomBytes(32);
@@ -55,7 +55,7 @@ public class ScryptKdfTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testCalibration() throws Exception {
+	public void testCalibration() {
 		Clock clock = new ArrayClock(
 				0, 50, // Duration for cost 256
 				0, 100, // Duration for cost 512
@@ -68,7 +68,7 @@ public class ScryptKdfTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testCalibrationChoosesMinCost() throws Exception {
+	public void testCalibrationChoosesMinCost() {
 		Clock clock = new ArrayClock(
 				0, 2000 // Duration for cost 256 is already too high
 		);

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

@@ -25,7 +25,7 @@ public class TagEncodingTest extends BrambleMockTestCase {
 	private final long streamNumber = 1234567890;
 
 	@Test
-	public void testKeyAffectsTag() throws Exception {
+	public void testKeyAffectsTag() {
 		Set<Bytes> set = new HashSet<>();
 		for (int i = 0; i < 100; i++) {
 			byte[] tag = new byte[TAG_LENGTH];
@@ -37,7 +37,7 @@ public class TagEncodingTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testProtocolVersionAffectsTag() throws Exception {
+	public void testProtocolVersionAffectsTag() {
 		Set<Bytes> set = new HashSet<>();
 		for (int i = 0; i < 100; i++) {
 			byte[] tag = new byte[TAG_LENGTH];
@@ -48,7 +48,7 @@ public class TagEncodingTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testStreamNumberAffectsTag() throws Exception {
+	public void testStreamNumberAffectsTag() {
 		Set<Bytes> set = new HashSet<>();
 		for (int i = 0; i < 100; i++) {
 			byte[] tag = new byte[TAG_LENGTH];

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

@@ -14,8 +14,7 @@ class TestAuthenticatedCipher implements AuthenticatedCipher {
 	private boolean encrypt = false;
 
 	@Override
-	public void init(boolean encrypt, SecretKey key, byte[] iv)
+	public void init(boolean encrypt, SecretKey key, byte[] iv) {
-			throws GeneralSecurityException {
 		this.encrypt = encrypt;
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/data/BdfReaderImplTest.java

@@ -557,10 +557,10 @@ public class BdfReaderImplTest extends BrambleTestCase {
 	@Test
 	public void testNestedListWithinDepthLimit() throws Exception {
 		// A list containing a list containing a list containing a list...
-		String lists = "";
+		StringBuilder lists = new StringBuilder();
-		for (int i = 1; i <= DEFAULT_NESTED_LIMIT; i++) lists += "60";
+		for (int i = 1; i <= DEFAULT_NESTED_LIMIT; i++) lists.append("60");
-		for (int i = 1; i <= DEFAULT_NESTED_LIMIT; i++) lists += "80";
+		for (int i = 1; i <= DEFAULT_NESTED_LIMIT; i++) lists.append("80");
-		setContents(lists);
+		setContents(lists.toString());
 		r.readList();
 		assertTrue(r.eof());
 	}
@@ -568,23 +568,23 @@ public class BdfReaderImplTest extends BrambleTestCase {
 	@Test(expected = FormatException.class)
 	public void testNestedListOutsideDepthLimit() throws Exception {
 		// A list containing a list containing a list containing a list...
-		String lists = "";
+		StringBuilder lists = new StringBuilder();
-		for (int i = 1; i <= DEFAULT_NESTED_LIMIT + 1; i++) lists += "60";
+		for (int i = 1; i <= DEFAULT_NESTED_LIMIT + 1; i++) lists.append("60");
-		for (int i = 1; i <= DEFAULT_NESTED_LIMIT + 1; i++) lists += "80";
+		for (int i = 1; i <= DEFAULT_NESTED_LIMIT + 1; i++) lists.append("80");
-		setContents(lists);
+		setContents(lists.toString());
 		r.readList();
 	}
 
 	@Test
 	public void testNestedDictionaryWithinDepthLimit() throws Exception {
 		// A dictionary containing a dictionary containing a dictionary...
-		String dicts = "";
+		StringBuilder dicts = new StringBuilder();
 		for (int i = 1; i <= DEFAULT_NESTED_LIMIT; i++)
-			dicts += "70" + "41" + "03" + "666F6F";
+			dicts.append("70" + "41" + "03" + "666F6F");
-		dicts += "11";
+		dicts.append("11");
 		for (int i = 1; i <= DEFAULT_NESTED_LIMIT; i++)
-			dicts += "80";
+			dicts.append("80");
-		setContents(dicts);
+		setContents(dicts.toString());
 		r.readDictionary();
 		assertTrue(r.eof());
 	}
@@ -592,13 +592,13 @@ public class BdfReaderImplTest extends BrambleTestCase {
 	@Test(expected = FormatException.class)
 	public void testNestedDictionaryOutsideDepthLimit() throws Exception {
 		// A dictionary containing a dictionary containing a dictionary...
-		String dicts = "";
+		StringBuilder dicts = new StringBuilder();
 		for (int i = 1; i <= DEFAULT_NESTED_LIMIT + 1; i++)
-			dicts += "70" + "41" + "03" + "666F6F";
+			dicts.append("70" + "41" + "03" + "666F6F");
-		dicts += "11";
+		dicts.append("11");
 		for (int i = 1; i <= DEFAULT_NESTED_LIMIT + 1; i++)
-			dicts += "80";
+			dicts.append("80");
-		setContents(dicts);
+		setContents(dicts.toString());
 		r.readDictionary();
 	}
 

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

@@ -28,6 +28,7 @@ import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
+@SuppressWarnings("TryFinallyCanBeTryWithResources")
 public abstract class BasicDatabaseTest extends BrambleTestCase {
 
 	private static final int BATCH_SIZE = 100;
@@ -47,7 +48,7 @@ public abstract class BasicDatabaseTest extends BrambleTestCase {
 
 	@Before
 	public void setUp() throws Exception {
-		testDir.mkdirs();
+		assertTrue(testDir.mkdirs());
 		Class.forName(getDriverName());
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/db/BasicH2Test.java

@@ -40,8 +40,7 @@ public class BasicH2Test extends BasicDatabaseTest {
 	}
 
 	@Override
-	protected void shutdownDatabase(File db, boolean encrypt)
+	protected void shutdownDatabase(File db, boolean encrypt) {
-			throws SQLException {
 		// The DB is closed automatically when the connection is closed
 	}
 }

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

@@ -53,7 +53,7 @@ public abstract class DatabaseMigrationTest extends BrambleMockTestCase {
 	protected final Clock clock = new SystemClock();
 
 	abstract Database<Connection> createDatabase(
-			List<Migration<Connection>> migrations) throws Exception;
+			List<Migration<Connection>> migrations);
 
 	@Before
 	public void setUp() {

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

@@ -29,7 +29,8 @@ public abstract class DatabasePerformanceComparisonTest
 	 * How many blocks of each condition to compare.
 	 */
 	private static final int COMPARISON_BLOCKS = 10;
-	private SecretKey databaseKey = getSecretKey();
+
+	private final SecretKey databaseKey = getSecretKey();
 
 	abstract Database<Connection> createDatabase(boolean conditionA,
 			DatabaseConfig databaseConfig, MessageFactory messageFactory,

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

@@ -20,10 +20,11 @@ import javax.annotation.Nullable;
 import static org.briarproject.bramble.test.TestUtils.deleteTestDirectory;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
 import static org.briarproject.bramble.util.IoUtils.copyAndClose;
+import static org.junit.Assert.assertTrue;
 
 public abstract class DatabaseTraceTest extends DatabasePerformanceTest {
 
-	private SecretKey databaseKey = getSecretKey();
+	private final SecretKey databaseKey = getSecretKey();
 
 	abstract Database<Connection> createDatabase(DatabaseConfig databaseConfig,
 			MessageFactory messageFactory, Clock clock);
@@ -39,7 +40,8 @@ public abstract class DatabaseTraceTest extends DatabasePerformanceTest {
 		populateDatabase(db);
 		db.close();
 		File traceFile = getTraceFile();
-		if (traceFile != null) traceFile.delete();
+		if (traceFile != null && traceFile.exists())
+			assertTrue(traceFile.delete());
 		db = openDatabase();
 		task.run(db);
 		db.close();

bramble-core/src/test/java/org/briarproject/bramble/db/H2DatabaseTraceTest.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.db;
 
 import org.briarproject.bramble.api.db.DatabaseConfig;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.junit.Ignore;
@@ -8,9 +9,8 @@ import org.junit.Ignore;
 import java.io.File;
 import java.sql.Connection;
 
-import javax.annotation.Nonnull;
-
 @Ignore
+@NotNullByDefault
 public class H2DatabaseTraceTest extends DatabaseTraceTest {
 
 	@Override
@@ -18,7 +18,6 @@ public class H2DatabaseTraceTest extends DatabaseTraceTest {
 			MessageFactory messageFactory, Clock clock) {
 		return new H2Database(databaseConfig, messageFactory, clock) {
 			@Override
-			@Nonnull
 			String getUrl() {
 				return super.getUrl() + ";TRACE_LEVEL_FILE=3";
 			}

bramble-core/src/test/java/org/briarproject/bramble/db/H2TransactionIsolationTest.java

@@ -20,6 +20,7 @@ import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
+@SuppressWarnings("TryFinallyCanBeTryWithResources")
 public class H2TransactionIsolationTest extends BrambleTestCase {
 
 	private static final String DROP_TABLE = "DROP TABLE foo IF EXISTS";
@@ -47,7 +48,7 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 	}
 
 	@After
-	public void tearDown() throws Exception {
+	public void tearDown() {
 		deleteTestDirectory(testDir);
 	}
 

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

@@ -92,7 +92,6 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	// All our transports use a maximum latency of 30 seconds
 	private static final int MAX_LATENCY = 30 * 1000;
 
-
 	private final SecretKey key = getSecretKey();
 	private final File testDir = getTestDirectory();
 	private final GroupId groupId;

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

@@ -25,7 +25,7 @@ public abstract class SingleDatabasePerformanceTest
 	abstract Database<Connection> createDatabase(DatabaseConfig databaseConfig,
 			MessageFactory messageFactory, Clock clock);
 
-	private SecretKey databaseKey = getSecretKey();
+	private final SecretKey databaseKey = getSecretKey();
 
 	@Override
 	protected void benchmark(String name,

bramble-core/src/test/java/org/briarproject/bramble/keyagreement/KeyAgreementProtocolTest.java

@@ -29,7 +29,7 @@ import static org.junit.Assert.assertThat;
 public class KeyAgreementProtocolTest extends BrambleTestCase {
 
 	@Rule
-	public JUnitRuleMockery context = new JUnitRuleMockery() {{
+	public final JUnitRuleMockery context = new JUnitRuleMockery() {{
 		// So we can mock concrete classes like KeyAgreementTransport
 		setImposteriser(ClassImposteriser.INSTANCE);
 	}};

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

@@ -327,6 +327,7 @@ public class LanTcpPluginTest extends BrambleTestCase {
 		assertEquals(0, comparator.compare(linkLocal, linkLocal));
 	}
 
+	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	private boolean systemHasLocalIpv4Address() throws Exception {
 		for (NetworkInterface i : list(getNetworkInterfaces())) {
 			for (InetAddress a : list(i.getInetAddresses())) {

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

@@ -165,7 +165,7 @@ public class SyncRecordReaderImplTest extends BrambleMockTestCase {
 		return new Record(PROTOCOL_VERSION, ACK, createPayload());
 	}
 
-	private Record createEmptyAck() throws Exception {
+	private Record createEmptyAck() {
 		return new Record(PROTOCOL_VERSION, ACK, new byte[0]);
 	}
 
@@ -173,7 +173,7 @@ public class SyncRecordReaderImplTest extends BrambleMockTestCase {
 		return new Record(PROTOCOL_VERSION, OFFER, createPayload());
 	}
 
-	private Record createEmptyOffer() throws Exception {
+	private Record createEmptyOffer() {
 		return new Record(PROTOCOL_VERSION, OFFER, new byte[0]);
 	}
 
@@ -181,7 +181,7 @@ public class SyncRecordReaderImplTest extends BrambleMockTestCase {
 		return new Record(PROTOCOL_VERSION, REQUEST, createPayload());
 	}
 
-	private Record createEmptyRequest() throws Exception {
+	private Record createEmptyRequest() {
 		return new Record(PROTOCOL_VERSION, REQUEST, new byte[0]);
 	}
 

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

@@ -7,7 +7,7 @@ import org.jmock.api.Invocation;
 public class RunAction implements Action {
 
 	@Override
-	public Object invoke(Invocation invocation) throws Throwable {
+	public Object invoke(Invocation invocation) {
 		Runnable task = (Runnable) invocation.getParameter(0);
 		task.run();
 		return null;

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

@@ -10,7 +10,6 @@ public class RunTransactionAction implements Action {
 
 	private final Transaction txn;
 
-	@SuppressWarnings("WeakerAccess")
 	public RunTransactionAction(Transaction txn) {
 		this.txn = txn;
 	}

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

@@ -1,5 +1,7 @@
 package org.briarproject.bramble.test;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.FileReader;
@@ -7,13 +9,12 @@ import java.io.IOException;
 import java.util.ArrayList;
 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;
 
+@NotNullByDefault
 public class UTest {
 
 	public enum Result {
@@ -158,8 +159,7 @@ public class UTest {
 	private static List<Double> readFile(String filename) {
 		List<Double> values = new ArrayList<>();
 		try {
-			BufferedReader in;
+			BufferedReader in = new BufferedReader(new FileReader(filename));
-			in = new BufferedReader(new FileReader(filename));
 			String s;
 			while ((s = in.readLine()) != null) values.add(new Double(s));
 			in.close();
@@ -185,8 +185,9 @@ public class UTest {
 			this.a = a;
 		}
 
+		@SuppressWarnings("UseCompareMethod")
 		@Override
-		public int compareTo(@Nonnull Value v) {
+		public int compareTo(Value v) {
 			if (value < v.value) return -1;
 			if (value > v.value) return 1;
 			return 0;

bramble-core/src/test/java/org/briarproject/bramble/util/ByteUtilsTest.java

@@ -33,11 +33,13 @@ public class ByteUtilsTest extends BrambleTestCase {
 
 	@Test(expected = IllegalArgumentException.class)
 	public void testReadUint16ValidatesArguments1() {
+		//noinspection ResultOfMethodCallIgnored
 		readUint16(new byte[1], 0);
 	}
 
 	@Test(expected = IllegalArgumentException.class)
 	public void testReadUint16ValidatesArguments2() {
+		//noinspection ResultOfMethodCallIgnored
 		readUint16(new byte[2], 1);
 	}
 
@@ -55,11 +57,13 @@ public class ByteUtilsTest extends BrambleTestCase {
 
 	@Test(expected = IllegalArgumentException.class)
 	public void testReadUint32ValidatesArguments1() {
+		//noinspection ResultOfMethodCallIgnored
 		readUint32(new byte[3], 0);
 	}
 
 	@Test(expected = IllegalArgumentException.class)
 	public void testReadUint32ValidatesArguments2() {
+		//noinspection ResultOfMethodCallIgnored
 		readUint32(new byte[4], 1);
 	}
 
@@ -79,11 +83,13 @@ public class ByteUtilsTest extends BrambleTestCase {
 
 	@Test(expected = IllegalArgumentException.class)
 	public void testReadUint64ValidatesArguments1() {
+		//noinspection ResultOfMethodCallIgnored
 		readUint64(new byte[7], 0);
 	}
 
 	@Test(expected = IllegalArgumentException.class)
 	public void testReadUint64ValidatesArguments2() {
+		//noinspection ResultOfMethodCallIgnored
 		readUint64(new byte[8], 1);
 	}
 

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

@@ -21,6 +21,7 @@ import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 
 import static com.sun.jna.Library.OPTION_FUNCTION_MAPPER;
@@ -163,11 +164,13 @@ class WindowsShutdownManagerImpl extends ShutdownManagerImpl {
 		}
 	}
 
+	@SuppressWarnings("UnusedReturnValue")
 	private interface User32 extends StdCallLibrary {
 
 		HWND CreateWindowEx(int styleEx, String className, String windowName,
-				int style, int x, int y, int width, int height, HWND parent,
+				int style, int x, int y, int width, int height,
-				HMENU menu, HINSTANCE instance, Pointer param);
+				@Nullable HWND parent, @Nullable HMENU menu,
+				@Nullable HINSTANCE instance, @Nullable Pointer param);
 
 		LRESULT DefWindowProc(HWND hwnd, int msg, WPARAM wp, LPARAM lp);
 
@@ -175,7 +178,8 @@ class WindowsShutdownManagerImpl extends ShutdownManagerImpl {
 
 		LRESULT SetWindowLongPtr(HWND hwnd, int index, WindowProc newProc);
 
-		int GetMessage(MSG msg, HWND hwnd, int filterMin, int filterMax);
+		int GetMessage(MSG msg, @Nullable HWND hwnd, int filterMin,
+				int filterMax);
 
 		boolean TranslateMessage(MSG msg);
 
@@ -184,6 +188,7 @@ class WindowsShutdownManagerImpl extends ShutdownManagerImpl {
 
 	private interface WindowProc extends StdCallCallback {
 
+		@SuppressWarnings("UnusedReturnValue")
 		LRESULT callback(HWND hwnd, int msg, WPARAM wp, LPARAM lp);
 	}
 }

bramble-java/src/main/java/org/briarproject/bramble/network/JavaNetworkManager.java

@@ -2,8 +2,7 @@ package org.briarproject.bramble.network;
 
 import org.briarproject.bramble.api.network.NetworkManager;
 import org.briarproject.bramble.api.network.NetworkStatus;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 
 import java.net.NetworkInterface;
 import java.net.SocketException;
@@ -19,8 +18,7 @@ import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 class JavaNetworkManager implements NetworkManager {
 
 	private static final Logger LOG =

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

@@ -22,6 +22,7 @@ import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
+import javax.annotation.concurrent.GuardedBy;
 
 import jssc.SerialPortEvent;
 import jssc.SerialPortEventListener;
@@ -63,9 +64,12 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
 	private final Condition connectedStateChanged = lock.newCondition();
 	private final Condition initialisedStateChanged = lock.newCondition();
 
-	// The following are locking: lock
+	@GuardedBy("lock")
 	private ReliabilityLayer reliability = null;
-	private boolean initialised = false, connected = false;
+	@GuardedBy("lock")
+	private boolean initialised = false;
+	@GuardedBy("lock")
+	private boolean connected = false;
 
 	private int lineLen = 0;
 

briar-android/src/main/java/im/delight/android/identicons/Identicon.java

@@ -19,12 +19,14 @@ package im.delight.android.identicons;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
-import android.support.annotation.NonNull;
 import android.support.annotation.UiThread;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
 import static android.graphics.Paint.Style.FILL;
 
 @UiThread
+@NotNullByDefault
 class Identicon {
 
 	private static final int ROWS = 9, COLUMNS = 9;
@@ -36,7 +38,7 @@ class Identicon {
 
 	private int cellWidth, cellHeight;
 
-	Identicon(@NonNull byte[] input) {
+	Identicon(byte[] input) {
 		if (input.length == 0) throw new IllegalArgumentException();
 		this.input = input;
 

briar-android/src/main/java/im/delight/android/identicons/IdenticonDrawable.java

@@ -20,19 +20,22 @@ import android.graphics.Canvas;
 import android.graphics.ColorFilter;
 import android.graphics.Rect;
 import android.graphics.drawable.Drawable;
-import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
 import static android.graphics.PixelFormat.OPAQUE;
 
 @UiThread
+@NotNullByDefault
 public class IdenticonDrawable extends Drawable {
 
 	private static final int HEIGHT = 200, WIDTH = 200;
 
 	private final Identicon identicon;
 
-	public IdenticonDrawable(@NonNull byte[] input) {
+	public IdenticonDrawable(byte[] input) {
 		super();
 		identicon = new Identicon(input);
 	}
@@ -48,7 +51,7 @@ public class IdenticonDrawable extends Drawable {
 	}
 
 	@Override
-	public void setBounds(@NonNull Rect bounds) {
+	public void setBounds(Rect bounds) {
 		super.setBounds(bounds);
 		identicon.updateSize(bounds.right - bounds.left,
 				bounds.bottom - bounds.top);
@@ -61,7 +64,7 @@ public class IdenticonDrawable extends Drawable {
 	}
 
 	@Override
-	public void draw(@NonNull Canvas canvas) {
+	public void draw(Canvas canvas) {
 		identicon.draw(canvas);
 	}
 
@@ -71,7 +74,7 @@ public class IdenticonDrawable extends Drawable {
 	}
 
 	@Override
-	public void setColorFilter(ColorFilter cf) {
+	public void setColorFilter(@Nullable ColorFilter cf) {
 
 	}
 

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

@@ -9,6 +9,7 @@ import android.app.PendingIntent;
 import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
+import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
 import android.support.annotation.UiThread;
 import android.support.v4.app.NotificationCompat;
@@ -21,8 +22,7 @@ import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.lifecycle.ServiceException;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
@@ -82,8 +82,7 @@ import static org.briarproject.briar.android.navdrawer.NavDrawerActivity.INTENT_
 import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
 
 @ThreadSafe
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 		Service, EventListener {
 
@@ -103,12 +102,12 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 	private final Multiset<GroupId> blogCounts = new Multiset<>();
 	private int introductionTotal = 0;
 	private int nextRequestId = 0;
+	@Nullable
 	private ContactId blockedContact = null;
+	@Nullable
 	private GroupId blockedGroup = null;
 	private boolean blockSignInReminder = false;
-	private boolean blockContacts = false, blockGroups = false;
+	private boolean blockBlogs = false;
-	private boolean blockForums = false, blockBlogs = false;
-	private boolean blockIntroductions = false;
 	private long lastSound = 0;
 
 	private volatile Settings settings = new Settings();
@@ -283,7 +282,6 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 
 	private void showContactNotification(ContactId c) {
 		androidExecutor.runOnUiThread(() -> {
-			if (blockContacts) return;
 			if (c.equals(blockedContact)) return;
 			contactCounts.add(c);
 			updateContactNotification(true);
@@ -385,7 +383,6 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 	@UiThread
 	private void showGroupMessageNotification(GroupId g) {
 		androidExecutor.runOnUiThread(() -> {
-			if (blockGroups) return;
 			if (g.equals(blockedGroup)) return;
 			groupCounts.add(g);
 			updateGroupMessageNotification(true);
@@ -456,7 +453,6 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 	@UiThread
 	private void showForumPostNotification(GroupId g) {
 		androidExecutor.runOnUiThread(() -> {
-			if (blockForums) return;
 			if (g.equals(blockedGroup)) return;
 			forumCounts.add(g);
 			updateForumPostNotification(true);
@@ -580,7 +576,6 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 
 	private void showIntroductionNotification() {
 		androidExecutor.runOnUiThread(() -> {
-			if (blockIntroductions) return;
 			introductionTotal++;
 			updateIntroductionNotification();
 		});

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

@@ -44,6 +44,7 @@ import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
 import static android.content.Intent.FLAG_ACTIVITY_NO_ANIMATION;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.support.v4.app.NotificationCompat.VISIBILITY_SECRET;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -57,11 +58,11 @@ import static org.briarproject.briar.api.android.LockManager.ACTION_LOCK;
 
 public class BriarService extends Service {
 
-	public static String EXTRA_START_RESULT =
+	public static final String EXTRA_START_RESULT =
 			"org.briarproject.briar.START_RESULT";
-	public static String EXTRA_NOTIFICATION_ID =
+	public static final String EXTRA_NOTIFICATION_ID =
 			"org.briarproject.briar.FAILURE_NOTIFICATION_ID";
-	public static String EXTRA_STARTUP_FAILED =
+	public static final String EXTRA_STARTUP_FAILED =
 			"org.briarproject.briar.STARTUP_FAILED";
 
 	private static final Logger LOG = getLogger(BriarService.class.getName());
@@ -110,7 +111,7 @@ public class BriarService extends Service {
 		// Create notification channels
 		if (SDK_INT >= 26) {
 			NotificationManager nm = (NotificationManager)
-					getSystemService(NOTIFICATION_SERVICE);
+					requireNonNull(getSystemService(NOTIFICATION_SERVICE));
 			NotificationChannel ongoingChannel = new NotificationChannel(
 					ONGOING_CHANNEL_ID,
 					getString(R.string.ongoing_notification_title),
@@ -178,8 +179,8 @@ public class BriarService extends Service {
 			i.putExtra(EXTRA_NOTIFICATION_ID, FAILURE_NOTIFICATION_ID);
 			b.setContentIntent(PendingIntent.getActivity(BriarService.this,
 					0, i, FLAG_UPDATE_CURRENT));
-			Object o = getSystemService(NOTIFICATION_SERVICE);
+			NotificationManager nm = (NotificationManager)
-			NotificationManager nm = (NotificationManager) o;
+					requireNonNull(getSystemService(NOTIFICATION_SERVICE));
 			nm.notify(FAILURE_NOTIFICATION_ID, b.build());
 			// Bring the dashboard to the front to clear the back stack
 			i = new Intent(BriarService.this, NavDrawerActivity.class);

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

@@ -7,7 +7,6 @@ import android.content.IntentFilter;
 import android.os.PowerManager;
 
 import org.briarproject.bramble.api.lifecycle.Service;
-import org.briarproject.bramble.api.lifecycle.ServiceException;
 import org.briarproject.briar.api.android.DozeWatchdog;
 
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -15,6 +14,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import static android.content.Context.POWER_SERVICE;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.os.PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED;
+import static java.util.Objects.requireNonNull;
 
 class DozeWatchdogImpl implements DozeWatchdog, Service {
 
@@ -32,14 +32,14 @@ class DozeWatchdogImpl implements DozeWatchdog, Service {
 	}
 
 	@Override
-	public void startService() throws ServiceException {
+	public void startService() {
 		if (SDK_INT < 23) return;
 		IntentFilter filter = new IntentFilter(ACTION_DEVICE_IDLE_MODE_CHANGED);
 		appContext.registerReceiver(receiver, filter);
 	}
 
 	@Override
-	public void stopService() throws ServiceException {
+	public void stopService() {
 		if (SDK_INT < 23) return;
 		appContext.unregisterReceiver(receiver);
 	}
@@ -49,8 +49,8 @@ class DozeWatchdogImpl implements DozeWatchdog, Service {
 		@Override
 		public void onReceive(Context context, Intent intent) {
 			if (SDK_INT < 23) return;
-			PowerManager pm =
+			PowerManager pm = (PowerManager)
-					(PowerManager) appContext.getSystemService(POWER_SERVICE);
+					requireNonNull(appContext.getSystemService(POWER_SERVICE));
 			if (pm.isDeviceIdleMode()) dozed.set(true);
 		}
 	}

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

@@ -38,6 +38,7 @@ public class NotificationCleanupService extends IntentService {
 	protected void onHandleIntent(@Nullable Intent i) {
 		if (i == null || i.getData() == null) return;
 		String uri = i.getData().toString();
+		//noinspection IfCanBeSwitch
 		if (uri.equals(CONTACT_URI)) {
 			notificationManager.clearAllContactNotifications();
 		} else if (uri.equals(GROUP_URI)) {

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

@@ -8,8 +8,7 @@ import com.vanniktech.emoji.emoji.Emoji;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.sync.Client;
@@ -29,8 +28,7 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.join;
 import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
 
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 class RecentEmojiImpl implements RecentEmoji, Client {
 
 	private static final Logger LOG =

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

@@ -44,8 +44,8 @@ public class StartupFailureActivity extends BaseActivity implements
 
 		// cancel notification
 		if (notificationId > -1) {
-			Object o = getSystemService(NOTIFICATION_SERVICE);
+			NotificationManager nm = (NotificationManager)
-			NotificationManager nm = (NotificationManager) requireNonNull(o);
+					requireNonNull(getSystemService(NOTIFICATION_SERVICE));
 			nm.cancel(notificationId);
 		}
 

briar-android/src/main/java/org/briarproject/briar/android/account/LockManagerImpl.java

@@ -14,8 +14,7 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.Service;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
@@ -34,6 +33,7 @@ import static android.app.AlarmManager.ELAPSED_REALTIME;
 import static android.app.PendingIntent.getService;
 import static android.content.Context.ALARM_SERVICE;
 import static android.os.SystemClock.elapsedRealtime;
+import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -44,8 +44,7 @@ import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_
 import static org.briarproject.briar.android.util.UiUtils.hasScreenLock;
 
 @ThreadSafe
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 public class LockManagerImpl implements LockManager, Service, EventListener {
 
 	private static final Logger LOG =
@@ -79,19 +78,19 @@ public class LockManagerImpl implements LockManager, Service, EventListener {
 		this.settingsManager = settingsManager;
 		this.notificationManager = notificationManager;
 		this.dbExecutor = dbExecutor;
-		this.alarmManager =
+		alarmManager = (AlarmManager)
-				(AlarmManager) appContext.getSystemService(ALARM_SERVICE);
+				requireNonNull(appContext.getSystemService(ALARM_SERVICE));
 		Intent i =
 				new Intent(ACTION_LOCK, null, appContext, BriarService.class);
-		this.lockIntent = getService(appContext, 0, i, 0);
+		lockIntent = getService(appContext, 0, i, 0);
-		this.timeoutNever = Integer.valueOf(
+		timeoutNever = Integer.valueOf(
 				appContext.getString(R.string.pref_lock_timeout_value_never));
-		this.timeoutDefault = Integer.valueOf(
+		timeoutDefault = Integer.valueOf(
 				appContext.getString(R.string.pref_lock_timeout_value_default));
-		this.timeoutMinutes = timeoutNever;
+		timeoutMinutes = timeoutNever;
 
 		// setting this in the constructor makes #getValue() @NonNull
-		this.lockable.setValue(false);
+		lockable.setValue(false);
 	}
 
 	@Override
@@ -145,7 +144,7 @@ public class LockManagerImpl implements LockManager, Service, EventListener {
 	@UiThread
 	@Override
 	public void checkIfLockable() {
-		boolean oldValue = lockable.getValue();
+		boolean oldValue = requireNonNull(lockable.getValue());
 		boolean newValue = hasScreenLock(appContext) && lockableSetting;
 		if (oldValue != newValue) {
 			this.lockable.setValue(newValue);
@@ -201,7 +200,8 @@ public class LockManagerImpl implements LockManager, Service, EventListener {
 	}
 
 	private boolean timeoutEnabled() {
-		return timeoutMinutes != timeoutNever && lockable.getValue();
+		return timeoutMinutes != timeoutNever
+				&& requireNonNull(lockable.getValue());
 	}
 
 	private boolean timedOut() {

briar-android/src/main/java/org/briarproject/briar/android/activity/BaseActivity.java

@@ -212,14 +212,16 @@ public abstract class BaseActivity extends AppCompatActivity
 	}
 
 	public void showSoftKeyboard(View view) {
-		Object o = getSystemService(INPUT_METHOD_SERVICE);
+		InputMethodManager im = (InputMethodManager)
-		((InputMethodManager) o).showSoftInput(view, SHOW_IMPLICIT);
+				getSystemService(INPUT_METHOD_SERVICE);
+		if (im != null) im.showSoftInput(view, SHOW_IMPLICIT);
 	}
 
 	public void hideSoftKeyboard(View view) {
 		IBinder token = view.getWindowToken();
-		Object o = getSystemService(INPUT_METHOD_SERVICE);
+		InputMethodManager im = (InputMethodManager)
-		((InputMethodManager) o).hideSoftInputFromWindow(token, 0);
+				getSystemService(INPUT_METHOD_SERVICE);
+		if (im != null) im.hideSoftInputFromWindow(token, 0);
 	}
 
 	@UiThread

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

@@ -54,9 +54,8 @@ abstract class BasePostFragment extends BaseFragment {
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
 		// retrieve MessageId of blog post from arguments
-		byte[] p = requireNonNull(getArguments()).getByteArray(POST_ID);
+		Bundle args = requireNonNull(getArguments());
-		if (p == null) throw new IllegalStateException("No post ID in args");
+		postId = new MessageId(requireNonNull(args.getByteArray(POST_ID)));
-		postId = new MessageId(p);
 
 		View view = inflater.inflate(R.layout.fragment_blog_post, container,
 				false);

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

@@ -1,5 +1,6 @@
 package org.briarproject.briar.android.blog;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.api.blog.BlogCommentHeader;
 import org.briarproject.briar.api.blog.BlogPostHeader;
 
@@ -7,9 +8,12 @@ import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
 
+import javax.annotation.concurrent.NotThreadSafe;
+
 import static java.util.Collections.sort;
 
-// This class is not thread-safe
+@NotThreadSafe
+@NotNullByDefault
 class BlogCommentItem extends BlogPostItem {
 
 	private static final BlogCommentComparator COMPARATOR =

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

@@ -167,7 +167,8 @@ public class BlogFragment extends BaseFragment
 	}
 
 	@Override
-	public void onActivityResult(int request, int result, Intent data) {
+	public void onActivityResult(int request, int result,
+			@Nullable Intent data) {
 		super.onActivityResult(request, result, data);
 
 		if (request == REQUEST_WRITE_BLOG_POST && result == RESULT_OK) {

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

@@ -7,13 +7,11 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.util.BriarAdapter;
 
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 class BlogPostAdapter extends BriarAdapter<BlogPostItem, BlogPostViewHolder> {
 
 	private final OnBlogPostClickListener listener;

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

@@ -1,9 +1,8 @@
 package org.briarproject.briar.android.blog;
 
-import android.support.annotation.NonNull;
-
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorInfo;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.blog.BlogPostHeader;
@@ -12,6 +11,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
 @NotThreadSafe
+@NotNullByDefault
 public class BlogPostItem implements Comparable<BlogPostItem> {
 
 	private final BlogPostHeader header;
@@ -67,16 +67,13 @@ public class BlogPostItem implements Comparable<BlogPostItem> {
 	}
 
 	@Override
-	public int compareTo(@NonNull BlogPostItem other) {
+	public int compareTo(BlogPostItem other) {
 		if (this == other) return 0;
 		return compare(getHeader(), other.getHeader());
 	}
 
 	protected static int compare(BlogPostHeader h1, BlogPostHeader h2) {
 		// The newest post comes first
-		long aTime = h1.getTimeReceived(), bTime = h2.getTimeReceived();
+		return Long.compare(h2.getTimeReceived(), h1.getTimeReceived());
-		if (aTime > bTime) return -1;
-		if (aTime < bTime) return 1;
-		return 0;
 	}
 }

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

@@ -2,7 +2,6 @@ package org.briarproject.briar.android.blog;
 
 import android.content.Context;
 import android.content.Intent;
-import android.support.annotation.NonNull;
 import android.support.annotation.UiThread;
 import android.support.v4.app.FragmentManager;
 import android.support.v4.view.ViewCompat;
@@ -14,6 +13,7 @@ import android.view.ViewGroup;
 import android.widget.ImageButton;
 import android.widget.TextView;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.view.AuthorView;
@@ -33,6 +33,7 @@ import static org.briarproject.briar.android.util.UiUtils.makeLinksClickable;
 import static org.briarproject.briar.api.blog.MessageType.POST;
 
 @UiThread
+@NotNullByDefault
 class BlogPostViewHolder extends RecyclerView.ViewHolder {
 
 	private final Context ctx;
@@ -44,13 +45,12 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 	private final ViewGroup commentContainer;
 	private final boolean fullText;
 
-	@NonNull
 	private final OnBlogPostClickListener listener;
 	@Nullable
 	private final FragmentManager fragmentManager;
 
 	BlogPostViewHolder(View v, boolean fullText,
-			@NonNull OnBlogPostClickListener listener,
+			OnBlogPostClickListener listener,
 			@Nullable FragmentManager fragmentManager) {
 		super(v);
 		this.fullText = fullText;

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

@@ -96,7 +96,8 @@ public class FeedFragment extends BaseFragment implements
 	}
 
 	@Override
-	public void onActivityResult(int requestCode, int resultCode, Intent data) {
+	public void onActivityResult(int requestCode, int resultCode,
+			@Nullable Intent data) {
 		super.onActivityResult(requestCode, resultCode, data);
 
 		// The BlogPostAddedEvent arrives when the controller is not listening

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

@@ -54,9 +54,7 @@ public class FeedPostFragment extends BasePostFragment {
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
 		Bundle args = requireNonNull(getArguments());
-		byte[] b = args.getByteArray(GROUP_ID);
+		blogId = new GroupId(requireNonNull(args.getByteArray(GROUP_ID)));
-		if (b == null) throw new IllegalStateException("No group ID in args");
-		blogId = new GroupId(b);
 
 		return super.onCreateView(inflater, container, savedInstanceState);
 	}

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

@@ -73,7 +73,6 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-
 		Bundle args = requireNonNull(getArguments());
 		GroupId blogId =
 				new GroupId(requireNonNull(args.getByteArray(GROUP_ID)));

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

@@ -8,6 +8,7 @@ import android.view.ViewGroup;
 import android.widget.ImageButton;
 import android.widget.TextView;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.util.BriarAdapter;
 import org.briarproject.briar.api.feed.Feed;
@@ -16,6 +17,7 @@ import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.briar.android.util.UiUtils.formatDate;
 
+@NotNullByDefault
 class RssFeedAdapter extends BriarAdapter<Feed, RssFeedAdapter.FeedViewHolder> {
 
 	private final RssFeedListener listener;
@@ -72,10 +74,7 @@ class RssFeedAdapter extends BriarAdapter<Feed, RssFeedAdapter.FeedViewHolder> {
 	@Override
 	public int compare(Feed a, Feed b) {
 		if (a == b) return 0;
-		long aTime = a.getAdded(), bTime = b.getAdded();
+		return Long.compare(b.getAdded(), a.getAdded());
-		if (aTime > bTime) return -1;
-		if (aTime < bTime) return 1;
-		return 0;
 	}
 
 	@Override

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

@@ -5,14 +5,14 @@ import android.support.v7.app.AlertDialog;
 import android.text.Editable;
 import android.text.TextWatcher;
 import android.util.Patterns;
-import android.view.Menu;
-import android.view.MenuItem;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.ProgressBar;
 
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
@@ -33,6 +33,8 @@ import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class RssFeedImportActivity extends BriarActivity {
 
 	private static final Logger LOG =
@@ -47,11 +49,10 @@ public class RssFeedImportActivity extends BriarActivity {
 	Executor ioExecutor;
 
 	@Inject
-	@SuppressWarnings("WeakerAccess")
 	volatile FeedManager feedManager;
 
 	@Override
-	public void onCreate(Bundle savedInstanceState) {
+	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
 		setContentView(R.layout.activity_rss_feed_import);
@@ -80,16 +81,6 @@ public class RssFeedImportActivity extends BriarActivity {
 		progressBar = findViewById(R.id.progressBar);
 	}
 
-	@Override
-	public boolean onCreateOptionsMenu(Menu menu) {
-		return super.onCreateOptionsMenu(menu);
-	}
-
-	@Override
-	public boolean onOptionsItemSelected(MenuItem item) {
-		return super.onOptionsItemSelected(item);
-	}
-
 	@Override
 	public void injectActivity(ActivityComponent component) {
 		component.inject(this);

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

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.blog;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.os.Bundle;
+import android.support.annotation.Nullable;
 import android.support.design.widget.Snackbar;
 import android.support.v7.app.AlertDialog;
 import android.support.v7.widget.LinearLayoutManager;
@@ -11,6 +12,8 @@ import android.view.MenuInflater;
 import android.view.MenuItem;
 
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
@@ -30,6 +33,8 @@ import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class RssFeedManageActivity extends BriarActivity
 		implements RssFeedListener {
 
@@ -40,11 +45,10 @@ public class RssFeedManageActivity extends BriarActivity
 	private RssFeedAdapter adapter;
 
 	@Inject
-	@SuppressWarnings("WeakerAccess")
 	volatile FeedManager feedManager;
 
 	@Override
-	public void onCreate(Bundle savedInstanceState) {
+	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
 		setContentView(R.layout.activity_rss_feed_manage);

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

@@ -36,6 +36,7 @@ import javax.inject.Inject;
 
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -70,9 +71,7 @@ public class WriteBlogPostActivity extends BriarActivity
 		super.onCreate(state);
 
 		Intent i = getIntent();
-		byte[] b = i.getByteArrayExtra(GROUP_ID);
+		groupId = new GroupId(requireNonNull(i.getByteArrayExtra(GROUP_ID)));
-		if (b == null) throw new IllegalStateException("No Group in intent.");
-		groupId = new GroupId(b);
 
 		setContentView(R.layout.activity_write_blog_post);
 

briar-android/src/main/java/org/briarproject/briar/android/contact/BaseContactListAdapter.java

@@ -1,10 +1,10 @@
 package org.briarproject.briar.android.contact;
 
 import android.content.Context;
-import android.support.annotation.NonNull;
 import android.view.View;
 
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.android.util.BriarAdapter;
 
 import javax.annotation.Nullable;
@@ -12,6 +12,7 @@ import javax.annotation.Nullable;
 import static android.support.v7.util.SortedList.INVALID_POSITION;
 import static org.briarproject.briar.android.util.UiUtils.getContactDisplayName;
 
+@NotNullByDefault
 public abstract class BaseContactListAdapter<I extends ContactItem, VH extends ContactItemViewHolder<I>>
 		extends BriarAdapter<I, VH> {
 
@@ -25,7 +26,7 @@ public abstract class BaseContactListAdapter<I extends ContactItem, VH extends C
 	}
 
 	@Override
-	public void onBindViewHolder(@NonNull VH ui, int position) {
+	public void onBindViewHolder(VH ui, int position) {
 		I item = items.get(position);
 		ui.bind(item, listener);
 	}

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListAdapter.java

@@ -5,8 +5,10 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
 
+@NotNullByDefault
 public class ContactListAdapter extends
 		BaseContactListAdapter<ContactListItem, ContactListItemViewHolder> {
 
@@ -28,22 +30,14 @@ public class ContactListAdapter extends
 	public boolean areContentsTheSame(ContactListItem c1, ContactListItem c2) {
 		// check for all properties that influence visual
 		// representation of contact
-		if (c1.getUnreadCount() != c2.getUnreadCount()) {
+		return c1.getUnreadCount() == c2.getUnreadCount() &&
-			return false;
+				c1.getTimestamp() == c2.getTimestamp() &&
-		}
+				c1.isConnected() == c2.isConnected();
-		if (c1.getTimestamp() != c2.getTimestamp()) {
-			return false;
-		}
-		return c1.isConnected() == c2.isConnected();
 	}
 
 	@Override
 	public int compare(ContactListItem c1, ContactListItem c2) {
-		long time1 = c1.getTimestamp();
+		return Long.compare(c2.getTimestamp(), c1.getTimestamp());
-		long time2 = c2.getTimestamp();
-		if (time1 < time2) return 1;
-		if (time1 > time2) return -1;
-		return 0;
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/contactselection/BaseContactSelectorFragment.java

@@ -53,11 +53,8 @@ public abstract class BaseContactSelectorFragment<I extends SelectableContactIte
 	@Override
 	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
-
 		Bundle args = requireNonNull(getArguments());
-		byte[] b = args.getByteArray(GROUP_ID);
+		groupId = new GroupId(requireNonNull(args.getByteArray(GROUP_ID)));
-		if (b == null) throw new IllegalStateException("No GroupId");
-		groupId = new GroupId(b);
 	}
 
 	@Override
@@ -65,7 +62,6 @@ public abstract class BaseContactSelectorFragment<I extends SelectableContactIte
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-
 		View contentView = inflater.inflate(R.layout.list, container, false);
 
 		list = contentView.findViewById(R.id.list);

briar-android/src/main/java/org/briarproject/briar/android/controller/SharingControllerImpl.java

@@ -59,6 +59,7 @@ public class SharingControllerImpl implements SharingController, EventListener {
 	}
 
 	private void setConnected(ContactId c) {
+		SharingListener listener = this.listener;
 		if (listener == null) return;
 		listener.runOnUiThreadUnlessDestroyed(() -> {
 			if (contacts.contains(c)) {

briar-android/src/main/java/org/briarproject/briar/android/conversation/AliasDialogFragment.java

@@ -3,7 +3,7 @@ package org.briarproject.briar.android.conversation;
 import android.arch.lifecycle.ViewModelProvider;
 import android.arch.lifecycle.ViewModelProviders;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.support.v7.app.AppCompatDialogFragment;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -12,6 +12,8 @@ import android.widget.Button;
 import android.widget.EditText;
 
 import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.BriarActivity;
 
@@ -19,6 +21,8 @@ import javax.inject.Inject;
 
 import static java.util.Objects.requireNonNull;
 
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class AliasDialogFragment extends AppCompatDialogFragment {
 
 	final static String TAG = AliasDialogFragment.class.getName();
@@ -34,7 +38,7 @@ public class AliasDialogFragment extends AppCompatDialogFragment {
 	}
 
 	@Override
-	public void onCreate(Bundle savedInstanceState) {
+	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
 		setStyle(STYLE_NO_TITLE, R.style.BriarDialogTheme);
@@ -45,8 +49,9 @@ public class AliasDialogFragment extends AppCompatDialogFragment {
 	}
 
 	@Override
-	public View onCreateView(@NonNull LayoutInflater inflater,
+	public View onCreateView(LayoutInflater inflater,
-			ViewGroup container, Bundle savedInstanceState) {
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
 		View v = inflater.inflate(R.layout.fragment_alias_dialog, container,
 				false);
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationViewModel.java

@@ -58,7 +58,7 @@ import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
 @NotNullByDefault
 public class ConversationViewModel extends AndroidViewModel {
 
-	private static Logger LOG =
+	private static final Logger LOG =
 			getLogger(ConversationViewModel.class.getName());
 	private static final String SHOW_ONBOARDING_IMAGE =
 			"showOnboardingImage";

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumActivity.java

@@ -88,7 +88,8 @@ public class ForumActivity extends
 	}
 
 	@Override
-	protected void onActivityResult(int request, int result, Intent data) {
+	protected void onActivityResult(int request, int result,
+			@Nullable Intent data) {
 		super.onActivityResult(request, result, data);
 
 		if (request == REQUEST_SHARE_FORUM && result == RESULT_OK) {

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumListAdapter.java

@@ -8,6 +8,7 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.util.BriarAdapter;
@@ -21,6 +22,7 @@ import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_NAME;
 import static org.briarproject.briar.android.util.UiUtils.formatDate;
 
+@NotNullByDefault
 class ForumListAdapter
 		extends BriarAdapter<ForumListItem, ForumListAdapter.ForumViewHolder> {
 

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumListFragment.java

@@ -94,9 +94,8 @@ public class ForumListFragment extends BaseEventFragment implements
 			@Nullable Bundle savedInstanceState) {
 		requireActivity().setTitle(R.string.forums_button);
 
-		View contentView =
+		View contentView = inflater.inflate(R.layout.fragment_forum_list,
-				inflater.inflate(R.layout.fragment_forum_list, container,
+				container, false);
-						false);
 
 		adapter = new ForumListAdapter(requireActivity());
 

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumListItem.java

@@ -4,7 +4,9 @@ import org.briarproject.briar.api.client.MessageTracker.GroupCount;
 import org.briarproject.briar.api.forum.Forum;
 import org.briarproject.briar.api.forum.ForumPostHeader;
 
-// This class is NOT thread-safe
+import javax.annotation.concurrent.NotThreadSafe;
+
+@NotThreadSafe
 class ForumListItem {
 
 	private final Forum forum;

briar-android/src/main/java/org/briarproject/briar/android/fragment/BaseFragment.java

@@ -63,6 +63,7 @@ public abstract class BaseFragment extends Fragment
 	}
 
 	public interface BaseFragmentListener {
+
 		@Deprecated
 		void runOnDbThread(Runnable runnable);
 

briar-android/src/main/java/org/briarproject/briar/android/fragment/ErrorFragment.java

@@ -11,6 +11,8 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 
+import static java.util.Objects.requireNonNull;
+
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -38,9 +40,7 @@ public class ErrorFragment extends BaseFragment {
 	@Override
 	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
-
+		Bundle args = requireNonNull(getArguments());
-		Bundle args = getArguments();
-		if (args == null) throw new AssertionError();
 		errorMessage = args.getString(ERROR_MSG);
 	}
 
@@ -49,8 +49,7 @@ public class ErrorFragment extends BaseFragment {
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-		View v = inflater
+		View v = inflater.inflate(R.layout.fragment_error, container, false);
-				.inflate(R.layout.fragment_error, container, false);
 		TextView msg = v.findViewById(R.id.errorMessage);
 		msg.setText(errorMessage);
 		return v;

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionActivity.java

@@ -2,8 +2,11 @@ package org.briarproject.briar.android.introduction;
 
 import android.content.Intent;
 import android.os.Bundle;
+import android.support.annotation.Nullable;
 
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
@@ -11,11 +14,13 @@ import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener
 
 import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
 
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class IntroductionActivity extends BriarActivity
 		implements BaseFragmentListener {
 
 	@Override
-	public void onCreate(Bundle savedInstanceState) {
+	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
 		Intent intent = getIntent();

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionMessageFragment.java

@@ -95,7 +95,6 @@ public class IntroductionMessageFragment extends BaseFragment
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-
 		// change toolbar text
 		ActionBar actionBar = introductionActivity.getSupportActionBar();
 		if (actionBar != null) {
@@ -126,11 +125,6 @@ public class IntroductionMessageFragment extends BaseFragment
 		return v;
 	}
 
-	@Override
-	public void onStart() {
-		super.onStart();
-	}
-
 	@Override
 	public String getUniqueTag() {
 		return TAG;

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/CameraView.java

@@ -16,8 +16,7 @@ import android.view.SurfaceView;
 import android.view.View;
 import android.view.WindowManager;
 
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 
 import java.io.IOException;
 import java.util.List;
@@ -43,8 +42,7 @@ import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @SuppressWarnings("deprecation")
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 		AutoFocusCallback, View.OnClickListener {
 
@@ -61,7 +59,9 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 	@Nullable
 	private Camera camera = null;
 	private int cameraIndex = 0;
+	@Nullable
 	private PreviewConsumer previewConsumer = null;
+	@Nullable
 	private Surface surface = null;
 	private int displayOrientation = 0, surfaceWidth = 0, surfaceHeight = 0;
 	private boolean previewStarted = false;
@@ -126,6 +126,7 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 		} catch (RuntimeException e) {
 			throw new CameraException(e);
 		}
+		requireNonNull(camera);
 		setDisplayOrientation(getScreenRotationDegrees());
 		// Use barcode scene mode if it's available
 		Parameters params = requireNonNull(camera).getParameters();
@@ -214,7 +215,7 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 	private void startConsumer() throws CameraException {
 		if (camera == null) throw new CameraException("Camera is null");
 		startAutoFocus();
-		previewConsumer.start(camera, cameraIndex);
+		requireNonNull(previewConsumer).start(camera, cameraIndex);
 	}
 
 	@UiThread
@@ -234,7 +235,7 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 	private void stopConsumer() throws CameraException {
 		if (camera == null) throw new CameraException("Camera is null");
 		cancelAutoFocus();
-		previewConsumer.stop();
+		requireNonNull(previewConsumer).stop();
 	}
 
 	@UiThread

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeActivity.java

@@ -22,6 +22,7 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import static android.widget.Toast.LENGTH_LONG;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -48,7 +49,8 @@ public class ContactExchangeActivity extends KeyAgreementActivity implements
 	@Override
 	public void onCreate(@Nullable Bundle state) {
 		super.onCreate(state);
-		getSupportActionBar().setTitle(R.string.add_contact_title);
+		requireNonNull(getSupportActionBar())
+				.setTitle(R.string.add_contact_title);
 	}
 
 	private void startContactExchange(KeyAgreementResult result) {
@@ -97,9 +99,8 @@ public class ContactExchangeActivity extends KeyAgreementActivity implements
 
 	@Override
 	public void contactExchangeFailed() {
-		runOnUiThreadUnlessDestroyed(() -> {
+		runOnUiThreadUnlessDestroyed(() ->
-			showErrorFragment(R.string.connection_error_explanation);
+				showErrorFragment(R.string.connection_error_explanation));
-		});
 	}
 
 	@UiThread

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeErrorFragment.java

@@ -18,6 +18,7 @@ import org.briarproject.briar.android.util.UiUtils;
 
 import javax.inject.Inject;
 
+import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.util.UiUtils.onSingleLinkClick;
 
 @MethodsNotNullByDefault
@@ -59,10 +60,7 @@ public class ContactExchangeErrorFragment extends BaseFragment {
 
 		// set humanized error message
 		TextView explanation = v.findViewById(R.id.errorMessage);
-		Bundle args = getArguments();
+		Bundle args = requireNonNull(getArguments());
-		if (args == null) {
-			throw new IllegalArgumentException("Use newInstance()");
-		}
 		explanation.setText(args.getString(ERROR_MSG));
 
 		// make feedback link clickable

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/IntroFragment.java

@@ -54,7 +54,6 @@ public class IntroFragment extends BaseFragment {
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-
 		View v = inflater.inflate(R.layout.fragment_keyagreement_id, container,
 				false);
 		scrollView = v.findViewById(R.id.scrollView);

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/QrCodeDecoder.java

@@ -5,6 +5,7 @@ import android.hardware.Camera.CameraInfo;
 import android.hardware.Camera.PreviewCallback;
 import android.hardware.Camera.Size;
 import android.os.AsyncTask;
+import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
 
 import com.google.zxing.BinaryBitmap;
@@ -16,9 +17,7 @@ import com.google.zxing.Result;
 import com.google.zxing.common.HybridBinarizer;
 import com.google.zxing.qrcode.QRCodeReader;
 
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 
 import java.util.logging.Logger;
 
@@ -28,8 +27,7 @@ import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 
 @SuppressWarnings("deprecation")
-@MethodsNotNullByDefault
+@NotNullByDefault
-@ParametersNotNullByDefault
 class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 
 	private static final Logger LOG = getLogger(QrCodeDecoder.class.getName());
@@ -37,6 +35,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	private final Reader reader = new QRCodeReader();
 	private final ResultCallback callback;
 
+	@Nullable
 	private Camera camera = null;
 	private int cameraIndex = 0;
 

briar-android/src/main/java/org/briarproject/briar/android/login/ChangePasswordActivity.java

@@ -1,7 +1,7 @@
 package org.briarproject.briar.android.login;
 
 import android.os.Bundle;
-import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.support.design.widget.TextInputLayout;
 import android.text.Editable;
 import android.text.TextWatcher;
@@ -15,6 +15,8 @@ import android.widget.TextView;
 import android.widget.TextView.OnEditorActionListener;
 import android.widget.Toast;
 
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
@@ -27,6 +29,8 @@ import static android.view.View.VISIBLE;
 import static org.briarproject.bramble.api.crypto.PasswordStrengthEstimator.QUITE_WEAK;
 import static org.briarproject.briar.android.util.UiUtils.setError;
 
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class ChangePasswordActivity extends BriarActivity
 		implements OnClickListener, OnEditorActionListener {
 
@@ -44,7 +48,7 @@ public class ChangePasswordActivity extends BriarActivity
 	private ProgressBar progress;
 
 	@Override
-	public void onCreate(Bundle state) {
+	public void onCreate(@Nullable Bundle state) {
 		super.onCreate(state);
 		setContentView(R.layout.activity_change_password);
 
@@ -127,7 +131,7 @@ public class ChangePasswordActivity extends BriarActivity
 				newPassword.getText().toString(),
 				new UiResultHandler<Boolean>(this) {
 					@Override
-					public void onResultUi(@NonNull Boolean result) {
+					public void onResultUi(Boolean result) {
 						if (result) {
 							Toast.makeText(ChangePasswordActivity.this,
 									R.string.password_changed,

briar-android/src/main/java/org/briarproject/briar/android/login/DozeFragment.java

@@ -76,7 +76,8 @@ public class DozeFragment extends SetupFragment
 	}
 
 	@Override
-	public void onActivityResult(int request, int result, Intent data) {
+	public void onActivityResult(int request, int result,
+			@Nullable Intent data) {
 		super.onActivityResult(request, result, data);
 		if (request == REQUEST_DOZE_WHITELISTING) {
 			if (!dozeView.needsToBeShown() || secondAttempt) {