Sample that is provided with javax.swing.JLayer class description is unusable.
http://download.java.net/jdk7/docs/api/javax/swing/JLayer.html

It contains several problems:

1) There's no way to take it and drop to main method of a simple "HelloWorld" class. Variable "frame" is undefined, frame size should be set and it should be shown.

2) A typo in "public void paint(Graphics g, JCompo nent c) {", there's an extra two spaces in arg type definition.

3) After corrections above JDK7b70 gives a compilation error:
Test.java:29: name clash: eventDispatched(AWTEvent,JLayer<JPanel>) in null and eventDispatched(AWTEvent,JLayer<? extends
 V>) in LayerUI have the same erasure, yet neither overrides the other
           public void eventDispatched(AWTEvent e, JLayer<JPanel> l) {
                       ^
  where V is a type-variable:
    V extends Component declared in class LayerUI
1 error

4) After fixing method "public void eventDispatched(AWTEvent e, JLayer<? extends JPanel> l)" executed sample won't work because mouse events will not be dispatched. An additional line:
layer.setLayerEventMask(AWTEvent.MOUSE_MOTION_EVENT_MASK);
should be added