The implementation of getListeners() for JComponent is broken for the following listeners:

PropertyChangeListener, AncestorListener, VetoableChangeListener

For the following test program, getListeners() will always return 0 no matter how many listeners you add to the component.

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import java.beans.*;
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;

public class TestGetListenersForJComponent
implements PropertyChangeListener, AncestorListener, VetoableChangeListener {

    JToolTip aComp = new JToolTip();
    EventListener[] eventListener;

    public TestGetListenersForJComponent() {
        eventListener = aComp.getListeners(PropertyChangeListener.class);
        System.out.println("PropertyChangeListener before adding a listener: " + eventListener.length);
        eventListener = aComp.getListeners(AncestorListener.class);
        System.out.println("AncestorListener before adding a listener: " + eventListener.length);
        eventListener = aComp.getListeners(VetoableChangeListener.class);
        System.out.println("VetoableChangeListener before adding a listener: " + eventListener.length);

        aComp.addPropertyChangeListener(this);
        aComp.addAncestorListener(this);
        aComp.addVetoableChangeListener(this);

        System.out.println("");

        eventListener = aComp.getListeners(PropertyChangeListener.class);
        System.out.println("PropertyChangeListener after adding a listener: " + eventListener.length);
        eventListener = aComp.getListeners(AncestorListener.class);
        System.out.println("AncestorListener after adding a listener: " + eventListener.length);
        eventListener = aComp.getListeners(VetoableChangeListener.class);
        System.out.println("VetoableChangeListener after adding a listener: " + eventListener.length);

    }

    public void propertyChange(PropertyChangeEvent e) {}

    public void ancestorAdded(AncestorEvent e) {}

    public void ancestorMoved(AncestorEvent event) {}

    public void ancestorRemoved(AncestorEvent event) {}

    public void vetoableChange(PropertyChangeEvent evt) {}

    public static void main(String[] args) {
        new TestGetListenersForJComponent();
    }
}        

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edmund.lou@eng 1999-07-27
JFC SQE