Callback should not be null.

components/net/sf/briar/plugins/file/UnixRemovableDriveMonitor.java

@@ -28,7 +28,7 @@ JNotifyListener {
 		}
 		synchronized(this) {
 			assert !started;
-			assert callback == null;
+			assert this.callback == null;
 			started = true;
 			this.callback = callback;
 			this.watches.addAll(watches);

test/net/sf/briar/plugins/file/PollingRemovableDriveMonitorTest.java

@@ -76,7 +76,11 @@ public class PollingRemovableDriveMonitorTest extends BriarTestCase {
 		// Create the monitor, start it, and give it some time to run
 		final RemovableDriveMonitor monitor = new PollingRemovableDriveMonitor(
 				Executors.newCachedThreadPool(), finder, 10);
-		monitor.start(null);
+		monitor.start(new Callback() {
+			public void driveInserted(File root) {
+				fail();
+			}
+		});
 		Thread.sleep(50);
 		// The monitor should rethrow the exception when it stops
 		try {

test/net/sf/briar/plugins/file/UnixRemovableDriveMonitorTest.java

@@ -26,19 +26,23 @@ public class UnixRemovableDriveMonitorTest extends BriarTestCase {
 
 	@Test
 	public void testNonexistentDir() throws Exception {
-		if(!OsUtils.isLinux() || OsUtils.isMacLeopardOrNewer()) {
+		if(!(OsUtils.isLinux() || OsUtils.isMacLeopardOrNewer())) {
 			System.err.println("Warning: Skipping test");
 			return;
 		}
 		File doesNotExist = new File(testDir, "doesNotExist");
 		RemovableDriveMonitor monitor = createMonitor(doesNotExist);
-		monitor.start(null);
+		monitor.start(new Callback() {
+			public void driveInserted(File root) {
+				fail();
+			}
+		});
 		monitor.stop();
 	}
 
 	@Test
 	public void testOneCallbackPerFile() throws Exception {
-		if(!OsUtils.isLinux() || OsUtils.isMacLeopardOrNewer()) {
+		if(!(OsUtils.isLinux() || OsUtils.isMacLeopardOrNewer())) {
 			System.err.println("Warning: Skipping test");
 			return;
 		}