Key bindings is sometimes to prefer over KeyListener

In Java (Swing) there are KeyListener:s and key bindins. KeyListerner is the classical way of catching events from the keyboard. But inn some situations the key bindings feature is preferred:

• If you want to catch (only) the CTRL key


• If you want to catch keys regardles of where the user has focus

For example if you are developing a tetris game this code can be used to get the Left arrow key:

        getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(
            KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), "left");
        getActionMap().put("left", new AbstractAction() {
            public void actionPerformed(ActionEvent e) {
                engine.moveBrickLeft();
            }
        });

To catch the control key use KeyStroke.getKeyStroke("ctrl pressed CONTROL") and KeyStroke.getKeyStroke("released CONTROL")

More information at http://java.sun.com/docs/books/tutorial/uiswing/misc/keybinding.html