In headless mode listeners that were added using method

 java.awt.Toolkit.addAWTEventListener(AWTEventListener listener, long eventMask)

are not returned by method

 java.awt.Toolkit.getAWTEventListeners(long eventMask)

Please see the following code sample (should be executed with VM arg "-Djava.awt.headless=true" )

----------------
import java.awt.event.AWTEventListener;
import java.awt.*;

public class Temp {

    public static void main(String[] args) {

        Toolkit toolkit = Toolkit.getDefaultToolkit();

        toolkit.addAWTEventListener(new AWTEventListener() {
            public void eventDispatched(AWTEvent event) { }
        }, AWTEvent.CONTAINER_EVENT_MASK);

        if ( toolkit.getAWTEventListeners(AWTEvent.CONTAINER_EVENT_MASK).length == 0 ) {
            throw new RuntimeException("An empty array returned unexpectedly");
        }
    }
}
----------------

The problem was cought by JCK QA on JDK7 b32

Due to this problem the following JCK test fails in Headless mode, but passes with display.
api/java_awt/Toolkit/index.html#GetAWTEventListeners[GetAWTEventListeners_4]: Failed. An empty array returned unexpectedly