/*
<applet code="TrafficLights.class" width="110" height="130">
</applet>
*/

import java.awt.*;
import java.applet.Applet;
import java.awt.event.*;

public class TrafficLights extends Applet {
    int light = (-1);   // Current light: 0 red, 1 yellow, 2 green,
                        //     3 blinking, (-1) all lights are off
    Button redButton;
    Button yellowButton;
    Button greenButton;
    Button blinkingButton;
    boolean blinkingOn = false; // Yellow light is On in blinking mode
    Thread blinkingThread = null;

    public void init() {
        setLayout(null);
        int x = 10;
        int y = 10;
        redButton = new Button("Red");
        redButton.setBounds(x, y, 60, 20);
        y += 30;
        add(redButton);

        yellowButton = new Button("Yellow");
        yellowButton.setBounds(x, y, 60, 20);
        y += 30;
        add(yellowButton);

        greenButton = new Button("Green");
        greenButton.setBounds(x, y, 60, 20);
        y += 30;
        add(greenButton);

        blinkingButton = new Button("Blinking");
        blinkingButton.setBounds(x, y, 60, 20);
        add(blinkingButton);

        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Object s = e.getSource();
                if (s == redButton)
                    onRed();
                else if (s == yellowButton)
                    onYellow();
                else if (s == greenButton)
                    onGreen();
                else if (s == blinkingButton)
                    onBlinking();
            }
        };

        redButton.addActionListener(al);
        yellowButton.addActionListener(al);
        greenButton.addActionListener(al);
        blinkingButton.addActionListener(al);

        setBackground(Color.gray);
    }

    void onRed() {
        light = 0;
        repaint();
    }

    void onYellow() {
        light = 1;
        repaint();
    }

    void onGreen() {
        light = 2;
        repaint();
    }

    void onBlinking() {
        if (light == 3) return;
        light = 3;
        Runnable b = new Runnable() {
            public void run() {
                blinkingOn = true;
                repaint();

                while (light == 3) {    // Loop until blinking is on
                    try {
                        Thread.sleep(1000);     // Wait 1 sec
                    } catch (InterruptedException e) {

                    }
                    blinkingOn = (!blinkingOn);
                    repaint(80, 40, 20, 20);    // Repaint the yellow lamp only
                }
            }
        };
        blinkingThread = new Thread(b);
        blinkingThread.start();
    }

    public void paint(Graphics g) {
        int x = 80;
        int y = 10;

        if (light == 0)
            g.setColor(Color.red);
        else
            g.setColor(Color.black);
        g.fillOval(x, y, 20, 20);
        y += 30;

        if (light == 1 || (light == 3 && blinkingOn))
            g.setColor(Color.yellow);
        else
            g.setColor(Color.black);
        g.fillOval(x, y, 20, 20);
        y += 30;

        if (light == 2)
            g.setColor(Color.green);
        else
            g.setColor(Color.black);
        g.fillOval(x, y, 20, 20);
    }
}