How to make jframe transparent?

Question

Hi
  some software's uses the monitor as a whiteboard to draw or to type text. How is this possible? I mean i thought that by making a  jframe (full screen) transparent we should be able to do this?   Is my understanding right? if so how to make the jframe transparent? when jframe is transparent will we be able to draw on it?

Answer 1

Try this:
public static void main(String[] args) {
  SwingUtilities.invokeLater(new Runnable() {
  @Override public void run() {
  JFrame f = new JFrame();
  f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  f.setUndecorated(true);
  f.setBackground(new Color(0,0,0,0));
  f.setExtendedState(JFrame.MAXIMIZED_BOTH);
  f.add(new JComponent() {
  @Override protected void paintComponent(Graphics g) {
  g.setColor(Color.BLUE);
  ((Graphics2D)g).setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
  g.fillOval(0, 0, getWidth(), getHeight());
  f.setVisible(true);
Message was edited by: 946128 in respose to PhHein's comment