Name: mgC56079 Date: 04/24/98



Javadoc says:

    /**
     * Replace the existing EventQueue with the specified one.
     * Any pending events are transferred to the new EventQueue
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     * for processing by it.
       ^^^^^^^^^^^^^^^^^^^^
     *
     * @param an EventQueue (or subclass thereof) instance to be used.
     */
    public synchronized void push(EventQueue newEventQueue) {
        synchronized (newEventQueue) {
            newEventQueue.queue = queue; // may be null
            newEventQueue.prev = this;
            next = newEventQueue;
        }
    }


---- Here is the test ----
import java.util.EmptyStackException;
import java.awt.*;

public class EventQueueTest1 {
  public static void main(String[] args) {
    EventQueue q1=new EventQueue();
    EventQueue q2=new EventQueue();
    LockDispatchThreadEvent locker1=new LockDispatchThreadEvent();
    LockDispatchThreadEvent locker2=new LockDispatchThreadEvent();

    // stop q1's dispatch thread.
    q1.postEvent(locker1);

    // this event will not be dispatched by q1 (dispatch thread is locked)
    q1.postEvent(new SomeEvent());

    // disable q2's dispatch thread.
    q2.postEvent(locker2);

    // wait until both threads are locked
    while (! (locker1.isDispatched() && locker2.isDispatched())) {
      Thread.yield();
    }

    // now push q2. Unprocessed SomeEvent should be passed to q2
    // (and should never be processed). However it will be processed by q1
    q1.push(q2);
    
    // unlock q1
    locker1.setLocked(false);

  }

}

class LockDispatchThreadEvent extends AWTEvent implements ActiveEvent {
  public LockDispatchThreadEvent() {
    super("",0);
  }

  boolean dispatched=false;
  boolean locked=true;

  public synchronized boolean isDispatched() {
    return dispatched;
  }

  public synchronized void setLocked(boolean locked) {
    this.locked=locked;
    notify();
  }

  public synchronized void dispatch() {
    dispatched=true;
    // this will disable dispatch thread
    while (locked) {
      System.out.println("Dispatch thread stopped: "+Thread.currentThread());
      try {
        wait();
      }
      catch (InterruptedException e) {
      }
    }
    System.out.println("Dispatch thread resumed: "+Thread.currentThread());

  }

}

class SomeEvent extends AWTEvent implements ActiveEvent {
  public SomeEvent() {
    super("",0);
  }

  public void dispatch() {
    System.out.println("Test failed: SomeEvent dispatched by "+Thread.currentThread());
  }

}
---- Sample run ----
% java EventQueueTest1
Dispatch thread stopped: Thread[AWT-EventQueue-0,5,main]
Dispatch thread stopped: Thread[AWT-EventQueue-1,5,main]
Dispatch thread resumed: Thread[AWT-EventQueue-0,5,main]
Test failed: SomeEvent dispatched by Thread[AWT-EventQueue-0,5,main]
^C


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