How to make one thread to wait for others in this situation?

Question

i am simulating a 2 phase locking system (shared and exclusive locks). multiple clients connects and requests for lock to a single server. at the server end, we have a class Server which implements Runnable interface. for each connection, a new Server object is created and a new thread is started. when a conflicting lock request is made by a client, the corresponding thread in the server end must wait until other threads corresponding to clients holding the lock releases it. and when all the locks in conflicting mode are released, the thread releasing the last conflicting lock must notify the waiting thread.
but the wait() and notifyAll() methods are not working as desired. i guess this is because each thread is working on different Server objects.
how can i implement the waiting and notifying mechanism?

Answer 1

Let me recap your question: your Server is a single resource to which
multiple Clients want access in a CREW (Concurrent Read Exclusive Write)
fashion. You need a single object somewhere that can serve as the
single monitor for locking. A Singleton object like this should do it:public class CREW {
   private static CREW crew= new CREW();
   public static getCREW() { return crew; }
   private boolean wite;
   private int read;
   public synchronized acquireReadLock() {
      // your read locking stuff here
   public synchronized acquireWriteLock() {
      // your write locking stuff here
}... the important part is that there is a single object to lock on. The
'acquire...' methods can be pooped up at will (a Command as a
parameter mayhap?)
kind regards,
Jos