Java JButton set tooltip text

import java.awt.FlowLayout;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Main extends JFrame {
  public Main() {
    super("JButton");

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLayout(new FlowLayout());

    JButton bn = new JButton("Close");
    bn.setToolTipText("Click this button to ...");
    getContentPane().add(bn);/*from   www. j av a 2  s. c  o m*/
  }

  public static void main(String[] args) {
    Main frame = new Main();
    frame.pack();
    frame.setVisible(true);
  }
}