/* Calculator.java */

import java.awt.*;
import java.awt.event.*;

public class Calculator
extends Frame
implements ActionListener
{
  private TextField tf;

  public Calculator()
  {
    super("Calculator");
    addWindowListener(new WindowClosingAdapter(true));
    setBackground(Color.lightGray);
    setLayout(new GridLayout(2, 1));
    tf = new TextField("777");
    add(tf);
    Panel p = new Panel();
    for (int i = 1; i <= 1000; i *= 10) {
      Button b = new Button("+" + i);
      b.addActionListener(this);
      p.add(b);
    }
    add(p);
  }

  public void actionPerformed(ActionEvent event)
  {
    String cmd = event.getActionCommand();
    int n1 = Integer.parseInt(tf.getText());
    int n2 = Integer.parseInt(cmd.substring(1));
    tf.setText("" + (n1 + n2));
  }

  public static void main(String[] args)
  {
    Calculator calc = new Calculator();
    calc.setLocation(100, 100);
    calc.setSize(200, 85);
    calc.setVisible(true);
  }
}