Focus Example

 public static void main(String[] args) {
        final JFrame frame = new JFrame();
        frame.setFocusable(true);
        frame.addKeyListener(new KeyListener() {

            @Override
            public void keyTyped(KeyEvent e) {
                System.out.println("KeyTyped");
            }

            @Override
            public void keyPressed(KeyEvent e) {
                System.out.println("KeyPressed");
            }

            @Override
            public void keyReleased(KeyEvent e) {
                System.out.println("KeyReleased");
            }
        });

        JPanel panel = new JPanel();
        frame.setContentPane(panel);
        JButton btn = new JButton("Button");

        btn.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Button gedrückt");
                frame.requestFocus();
            }
        });
        panel.add(btn);
        frame.setSize(300, 300);
        frame.setVisible(true);
    }