Improved encapsulation of thread synchronisation as follows

- replaced use of Object instance mutex with a private final Lock object
- replaced Object signaling with specific condition signalling

briar-desktop/src/org/briarproject/plugins/file/UnixRemovableDriveMonitor.java

@@ -4,6 +4,9 @@ import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 import net.contentobjects.jnotify.JNotify;
 import net.contentobjects.jnotify.JNotifyListener;
@@ -21,7 +24,11 @@ JNotifyListener {
 	private Callback callback = null; // Locking: this
 
 	protected abstract String[] getPathsToWatch();
-
+	
+	//TODO: rationalise this in a further refactor
+	private final Lock synchLock = new ReentrantLock();
+	private static final Lock staticSynchLock = new ReentrantLock();
+	
 	private static Throwable tryLoad() {
 		try {
 			Class.forName("net.contentobjects.jnotify.JNotify");
@@ -33,12 +40,18 @@ JNotifyListener {
 		}
 	}
 
-	public static synchronized void checkEnabled() throws IOException {
-		if(!triedLoad) {
-			loadError = tryLoad();
-			triedLoad = true;
+	public static void checkEnabled() throws IOException {
+		staticSynchLock.lock();
+		try {
+			if(!triedLoad) {
+				loadError = tryLoad();
+				triedLoad = true;
+			}
+			if(loadError != null) throw new IOException(loadError.toString());
+		} 
+		finally{
+			staticSynchLock.unlock();
 		}
-		if(loadError != null) throw new IOException(loadError.toString());
 	}
 
 	public void start(Callback callback) throws IOException {
@@ -49,34 +62,46 @@ JNotifyListener {
 			if(new File(path).exists())
 				watches.add(JNotify.addWatch(path, mask, false, this));
 		}
-		synchronized(this) {
-			assert !started;
-			assert this.callback == null;
-			started = true;
-			this.callback = callback;
-			this.watches.addAll(watches);
-		}
+			synchLock.lock();
+			try {
+				assert !started;
+				assert this.callback == null;
+				started = true;
+				this.callback = callback;
+				this.watches.addAll(watches);
+			} 
+			finally{
+				synchLock.unlock();
+			}
 	}
 
 	public void stop() throws IOException {
 		checkEnabled();
 		List<Integer> watches;
-		synchronized(this) {
-			assert started;
-			assert callback != null;
-			started = false;
-			callback = null;
-			watches = new ArrayList<Integer>(this.watches);
-			this.watches.clear();
-		}
+			synchLock.lock();
+			try {
+				assert started;
+				assert callback != null;
+				started = false;
+				callback = null;
+				watches = new ArrayList<Integer>(this.watches);
+				this.watches.clear();
+			} 
+			finally{
+				synchLock.unlock();
+			}
 		for(Integer w : watches) JNotify.removeWatch(w);
 	}
 
 	public void fileCreated(int wd, String rootPath, String name) {
 		Callback callback;
-		synchronized(this) {
-			callback = this.callback;
-		}
+			synchLock.lock();
+			try {
+				callback = this.callback;
+			} 
+			finally{
+				synchLock.unlock();
+			}
 		if(callback != null)
 			callback.driveInserted(new File(rootPath + "/" + name));
 	}