You are stuck in wait() until another thread invokes notify() on the
same object (in your example, the object referred to as "this"). It
should do that after modifying the ArrayList whose size you are
checking.

/gordon

--

In addition to the previous response, if you're filling up the list
and emptying it once, you might look at a CountDownLatch as a more
convenient way to wait for the list to become empty.

I'm struggling getting my head around this for some reason today. I'm not
referring to things correctly i n my code, with respect to the threads -- I
must be misunderstanding you Gordon, because I am getting and
IllegalMonitorStateException when I call notify on the runnable, from, what
I believe, is the class that owns the Runnable, yes? I've pared down the
code here, but you can see what is going on. What am I missing? The thread
calling the notify IS the Event Dispatch thread, isn;t it? If not, how do I
obtain it from where I am at below? Thanks again -- I'm just dizzy from this
or something! -Ralph

Exception in thread "AWT-EventQueue-0"
java.lang.IllegalMonitorStateException: current thread not owner
       at java.lang.Object.notify(Native Method)
       at
robot.server.core.responder.SmartResponder.getGoBack(SmartResponder.java:411)

public class SmartResponder {
   public Runnable studyinteractive;
...
   public void doResponseStudy() {
       studyinteractive = new Runnable(){
           public void run(){
               study();
           };
       };
       javax.swing.SwingUtilities.invokeLater(studyinteractive);
   }
   public void study(){
       ...
                try{
                   synchronized(this) {
                       while(getGoBack())
                           wait();
                   }
               }catch(InterruptedException interruptedexception) { }
   }
   public boolean getGoBack(){ //pared down here, b is actually a long
conditional, not merely what is shown
       boolean b= arrayList.size()>0;
       if(!b )
           studyinteractive.notify(); //// <-----------line 411
       return b;
   }