//新建一個button
JButton bt = new JButton（）；
//新增監聽
bt.addMouseMotionListener(new MouseAdapter(){  
	       public void mouseMoved(MouseEvent e) {  
	               bt .setToolTipText("你想要顯示的內容");
	           }  
	       }  
	   });

import javax.swing.JFrame;
import java.awt.Dimension;
import javax.swing.JPanel;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import java.awt.Rectangle;

public class HideButton extends JFrame {

 private JPanel jPanel = null;
 private JButton jButton = null;

 /**
  * This method initializes 
  * 
  */
 public HideButton() {
  super();
  initialize();
 }

 /**
  * This method initializes this
  * 
  */
 private void initialize() {
        this.setSize(new Dimension(239, 129));
        this.setContentPane(getJPanel());
  this.setVisible(true);
  this.setDefaultCloseOperation(EXIT_ON_CLOSE);
 }

 /**
  * This method initializes jPanel 
  *  
  * @return javax.swing.JPanel 
  */
 private JPanel getJPanel() {
  if (jPanel == null) {
   jPanel = new JPanel();
   jPanel.setLayout(null);
   jPanel.add(getJButton(), null);
  }
  return jPanel;
 }

 /**
  * This method initializes jButton 
  *  
  * @return javax.swing.JButton 
  */
 private JButton getJButton() {
  if (jButton == null) {
   jButton = new JButton();
   jButton.setBounds(new Rectangle(72, 29, 109, 39));
   jButton.addMouseListener(new java.awt.event.MouseAdapter() {
    public void mouseEntered(java.awt.event.MouseEvent e) {
     jButton.setVisible(false);
    }
public void mouseExited(java.awt.event.MouseEvent e) {    
     jButton.setVisible(true);
    }
   });
  }
  return jButton;
 }
 public static void main(String args[]){
  new HideButton().setVisible(true);
 }
}