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

public class PlayBalloon extends Frame 
    implements ActionListener, WindowListener {

    private Button grow, shrink;
    private Balloon myBalloon;

    public static void main(String[] args) {
        PlayBalloon f = new PlayBalloon();
        f.setSize(300, 200);
        f.setVisible(true);
    }

    public PlayBalloon() {

        setTitle("Balloon");

        setLayout(new FlowLayout());

        grow = new Button("Grow");
        add(grow);

        shrink = new Button("Shrink");
        add(shrink);

        myBalloon = new Balloon(20, 50, 50);
    }

    public void actionPerformed(ActionEvent event) {
        if (event.getSource() == grow)
            myBalloon.changeSize(10);
        if (event.getSource() == shrink)
            myBalloon.changeSize(-10);
        repaint();
    }

    public void windowClosing(WindowEvent e) {
        System.exit(0);
    }

    public void windowIconified(WindowEvent e) {
    }
    public void windowOpened(WindowEvent e) {
    }
    public void windowClosed(WindowEvent e) {
    }
    public void windowDeiconified(WindowEvent e) {
    }
    public void windowActivated(WindowEvent e) {
    }
    public void windowDeactivated(WindowEvent e) {
    } 

    public void paint (Graphics g) {
        myBalloon.display(g);
    }
}

class Balloon {

    private int diameter;
    private int xCoord, yCoord;

    Balloon(int initialDiameter, int initialX, int initialY) {
        diameter = initialDiameter;
        xCoord = initialX;
        yCoord = initialY;
    }

    public void changeSize(int change) {
        diameter = diameter + change;
    }

    public void display(Graphics g) {
        g.drawOval(xCoord, yCoord, diameter, diameter);
    }
}