import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class Compute
{
  public Compute ()
  {
    JFrame frame = new JFrame("Event Test");
    Container content = frame.getContentPane();
    content.setLayout(new FlowLayout());
    frame.setSize(300,300);

    final JTextField tf = new JTextField(10);
    content.add(tf);
    final JLabel label = new JLabel();
    content.add(label);
    final JButton button = new JButton("Compute");
    content.add(button);

    ActionListener al = new ActionListener() {
      public void actionPerformed(ActionEvent ae)
      {
        String text = tf.getText();
        int value = 0;
        try
        {
          value = Integer.parseInt(text);
        }
        catch (NumberFormatException nfe)
        {
          return;
        }
        label.setText(String.valueOf(value * value));
      }
    };

    button.addActionListener(al);
    
    frame.setVisible(true);
  }
  
  public static void main(String[] args)
  {
    new Compute();
  }
}