Cleaner menu selection handling

• No interest in actions for MenuBar and Menu - only in MenuItem.
• Define a new subclass of MenuItem, MenuButton with one method action()

      public boolean action(Event evt, Object what) {
          return false;
      }
  

• Subclass menu buttons from this, with application logic in action()

  class QuitButton extends MenuButton {
      public boolean action(Event evt, Object what) {
          System.out.println("Exiting...");
          exit();
          return true;
      }
  }
  

• Override Frame action() only enough to invoke action() method on subclasses of MenuButton

  public class MyFrame extends Frame {
      public boolean action(Event evt, Object what) {
          if (evt.target instanceof MenuButton) {
              return ((MenuButton) evt.target).action(evt, what);
          } else {
              return super.action(evt, what);
          }
      }
  }