JAVA APPLET PROGRAM TO SIMULATE TRAFFIC LIGHTS

Program Statement: Write a JAVA program that simulates a traffic light. The program lets the user select one of the three lights: red, yellow, green. When a radio button is selected, the light is turned on, and only one light can be on at a time. No light is on when the program starts.

Tested on:

Software: Windows 8, Jdk 1.6,   Netbeans IDE

Hardware: Intel Core i3, 4 GB RAM, 500 GB HDD

Source Code

@Author: Praveen Kanwar
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
/* <applet code="TrafficLights" width=500 height=500> </applet> */
public class TrafficLights extends Applet implements ItemListener
{
    CheckboxGroup cbg;
    Checkbox r,g1,y;
    public void init()
    {
        cbg=new CheckboxGroup();
        r=new Checkbox("Red",cbg,false);
        g1=new Checkbox("Green",cbg,false);
        y=new Checkbox("Yellow",cbg,false);
        r.addItemListener(this);
        g1.addItemListener(this);
        y.addItemListener(this);
        add(r);
        add(g1);
        add(y);
    }
    public void itemStateChanged(ItemEvent ie)
    {
        repaint();
    }
    public void paint(Graphics g)
    {
        if(cbg.getSelectedCheckbox()==r)
        {
            g.setColor(Color.red);
            g.fillOval(150, 125,70,70);
        }
        if(cbg.getSelectedCheckbox()==g1)
        {
            g.setColor(Color.green);
            g.fillOval(150, 125,70,70);
        }
        if(cbg.getSelectedCheckbox()==y)
        {
            g.setColor(Color.yellow);
            g.fillOval(150, 125,70,70);
        }
    }
}

Output