Re: How can a JFrame be aware of keys pressed within controls?

The simple use of generics takes about five minutes to learn. You simply
add the base type for generic classes or methods within angle brackets
(<>).

The fundamental insight for me about generics is that it comprises
assertions about type relationships, not instructions. I view it as a
declarative (that is, non-procedural) sub-language.

Check out the Javadocs for 'getFocusTraversalKeys()', which of course you
would have looked up anyway:
<http://java.sun.com/javase/6/docs/api/java/awt/Container.html#getFocusTraversalKeys(int)>

You will immediately observe that it returns 'Set<AWTKeyStroke>'. So you
simply use that same exact type, copy and paste, for the return value in
your own code, and voil?, you're using generics!

 class ToggleEnter
 {
  public static void activate( Container c )
  {
    Set <AWTKeyStroke> forwardKeys =
      c.getFocusTraversalKeys(
KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS );

    Set <AWTKeyStroke> newForwardKeys =
       new HashSet <AWTKeyStroke> ( forwardKeys );

    newForwardKeys.add( KeyStroke.getKeyStroke(KeyEvent.VK_ENTER, 0) );

    c.setFocusTraversalKeys(
      KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, newForwardKeys );
  }

etc.

The advantage is increased type safety enforced at compile time.