Java Swing

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextField;

public class TestSwing extends JFrame
{
 JButton b;
 JTextField tf;
 public TestSwing()
 {
  b = new JButton("TEST");
  this.add(b);
  tf = new JTextField(20);
  this.add(tf);
  this.setLayout(new FlowLayout());
  this.setBounds(200,100,300,150);
  this.setVisible(true);
  b.addActionListener(new ActionListener()
  {
   public void actionPerformed(ActionEvent e)
   {
    String s = JOptionPane.showInputDialog("Please input:","1");
    tf.setText(s);
   }
  });
 }
 public static void main(String[] args)
 {
  TestSwing st = new TestSwing();
 }
}