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

public class Applet extends JApplet implements ActionListener {
    private JTextField indata = new JTextField(10);
    private JButton plusButton = new JButton("+");
    private JTextField resultat = new JTextField(10);
    private int summa = 0;

    public void actionPerformed(ActionEvent event) {
        String s = indata.getText();
        try {
            int n = Integer.parseInt(s);
	    summa = summa + n;
            resultat.setText(summa + "");
        }
        catch (NumberFormatException exc) {
            resultat.setText("ERROR");
        }
    } // actionPerformed

    public void init() {
        plusButton.addActionListener(this);
        Container cp = getContentPane();
        cp.setLayout(new FlowLayout());
        cp.add(indata);
        cp.add(plusButton);
        cp.add(resultat);
	resultat.setText(summa + "");
    }

    public static void main(String[] args) {
        Applet applet = new Applet();
        JFrame frame = new JFrame("Applet");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(applet);
        frame.setSize(160, 100);
        applet.init();
        applet.start();
        frame.setVisible(true);
    }
} // class Applet