Re: Making one or more threads wait for another to produce a value or fail

Try #2. I've added "deliverOne()" and "deliverAll()" to distinguish
between a message sent to a single thread, and a message sent to all
threads.

However, this doesn't seem to meet your requirement for an exception.
So I've added also "deliverException()" which is basically the same as
"deliverAll()" except with the semantic that the receiver sees an
exception thrown rather than seeing a return value.

Again this is untested. Batter running low! Back later!

package test;

public class BroadcastSynchronizer<V, E extends Throwable> {

     private volatile E exception;
     private volatile V verdict;
     private final Object lock = new Object();

     public V await() throws E, InterruptedException {
         while( verdict == null && exception == null ) {
             synchronized( lock ) {
                 if( verdict == null && exception == null )
                     lock.wait();
             }
         }
         if( exception != null ) {
             throw exception;
         }
         return verdict;
     }

     public void deliverAll( V verdict ) {
         this.verdict = verdict;
         synchronized( lock ) {
            lock.notifyAll();
         }
     }

     public void deliverOne( V verdict ) {
         this.verdict = verdict;
         synchronized( lock ) {
            lock.notify();
         }
     }

     public void deliverException( E exception ) {
         this.exception = exception;
         synchronized( lock ) {
            lock.notifyAll();
         }
     }
}