Displaying tooltip programmatically

Question

Hello,
I found code in the forum (How to force the display of a ToolTip? for the above mentioned task. The posting is of this year, but when I try to apply the code, my toolTipAction is always null. Is there a mistake in my code or a change in jdk7?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class TTTest extends JFrame {
  public TTTest() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container cp= getContentPane();
    cp.setLayout(null);
    setSize(260,300);
    final JTextField tf= new JTextField();
    tf.setToolTipText("This is the tooltip.");
    tf.setBounds(75,80,100,25);
    JButton b= new JButton("Display tooltip");
    b.setBounds(50,150,150,30);
    b.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent event) {
     Action toolTipAction = tf.getActionMap().get("postTip");
     if (toolTipAction != null) {
       ActionEvent postTip = new ActionEvent(tf, ActionEvent.ACTION_PERFORMED, "");
       toolTipAction.actionPerformed(postTip);
     else {
//       Since toolTipAction is null, let's inspect the map
       ActionMap map = tf.getActionMap();
       Object[] keys = map.allKeys();
       for (Object o: keys) {
//         System.out.println(o); // Indeed, there's no "postTip" key.
         if (o.equals("postTip")) System.out.println("--- KEY FOUND! ---");
    cp.add(tf);
    cp.add(b);
    setVisible(true);
  static public void main(String args[]) {
    EventQueue.invokeLater(new Runnable() {
      public void run() {
     new TTTest();
  }

Answer 1

That's convincing. Thank you very much.
... why that unnecessary local field cp?I only remember that when it became possible to add components directlly to a JFrame (was it 1.5?)
that there are still some cases when the contentPane is a must. So when testing I prefer to be on the safe side.
In the meantime I found this way:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class TTTest2 extends JFrame {
  private Popup tooltipPopup;
  public TTTest2() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLayout(new FlowLayout(FlowLayout.CENTER, 60, 60));
    setSize(260,300);
    final JTextField tf= new JTextField(10);
    final PopupFactory popupFactory = PopupFactory.getSharedInstance();
    final JToolTip toolTip = new JToolTip();
    toolTip.setTipText("This is the tooltip.");
    JButton b= new JButton("Display tooltip");
    b.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent event) {
     tooltipPopup = popupFactory.getPopup(tf, toolTip,
                         tf.getLocationOnScreen().x +10,
                         tf.getLocationOnScreen().y +25);
//     tooltipPopup.show(); // if you want to programmatically close the tip.
     showTooltip(3);
    add(tf);
    add(b);
    setVisible(true);
  private void showTooltip(int seconds) {
    tooltipPopup.show();
    javax.swing.Timer t= new javax.swing.Timer(seconds*1000, new ActionListener() {
      public void actionPerformed(ActionEvent e) {
     tooltipPopup.hide(); // disposes of the popup.
    t.setRepeats(false);
    t.start();
  static public void main(String args[]) {
    EventQueue.invokeLater(new Runnable() {
      public void run() {
     new TTTest2();
}