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

public class SimpleGUI4 extends JFrame implements ActionListener {
    
    private JTextField data;
    private JButton[] numKeys;
    
    public SimpleGUI4() {
        setTitle("Simple GUI #4");
        getContentPane().setBackground(new Color(0, 0, 255));
        getContentPane().setLayout(new GridLayout(3,2));
        
        numKeys = new JButton[5];
        
        for (int i = 0; i < numKeys.length; ++i) {
            numKeys[i] = new JButton(Integer.toString(i+1));
            numKeys[i].addActionListener(this);
            getContentPane().add(numKeys[i]);
        }

        data = new JTextField(10);
        getContentPane().add(data);
    }

    public void actionPerformed(ActionEvent e) {
        int num = 0;
        while (num < numKeys.length && e.getSource() != numKeys[num]) {
            ++num;
        }
        data.setText(data.getText() + Integer.toString(num+1));
    }

    public static void main(String[] args) {
        SimpleGUI4 sg = new SimpleGUI4();
        sg.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        sg.setSize(400, 300);
        sg.setVisible(true);    
    }
}