Question

Write a program that simulates a traffic light. When a radio button is selected, the corresponding light is turned on, and only one light can be on at a time. No light is on when the program starts. Use Group instead of Pane to combine shapes, and then put the group to the center of a BorderPane will make all shapes staying in center when resizing the window.

using NetBeans Java

Answer 1

Java Code for the given question:

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Dimension;

import java.awt.FlowLayout;

import java.awt.Graphics;

import java.awt.event.ActionEvent;

import java.awt.event.ItemListener;

import java.awt.event.ItemEvent;

import javax.swing.ButtonGroup;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JRadioButton;

public class Name extends JFrame implements ItemListener{

   //Create buttons for traffic light

   private JRadioButton jrbRed;

   private JRadioButton jrbYellow;

   private JRadioButton jrbGreen;

   private ButtonGroup btg = new ButtonGroup();

   //create class light

   private Name.Light light = new Name.Light();

   public static void main(String[] args){

       //Create frame

       Name frame = new Name();

       frame.setDefaultCloseOperation(3);

       frame.setSize(250, 170);

       frame.setLocationRelativeTo(null);

       frame.setVisible(true);

   }

   public Name(){

       setTitle("Traffic Lights");

       JPanel p1 = new JPanel();

       p1.setLayout(new FlowLayout(1));

       p1.add(this.light);

       JPanel p2 = new JPanel();

       p2.setLayout(new FlowLayout());

       p2.add(this.jrbRed = new JRadioButton("Red"));

       p2.add(this.jrbYellow = new JRadioButton("Yellow"));

       p2.add(this.jrbGreen = new JRadioButton("Green"));

       this.jrbRed.setMnemonic('R');

       this.jrbYellow.setMnemonic('Y');

       this.jrbGreen.setMnemonic('G');

       this.btg.add(this.jrbRed);

       this.btg.add(this.jrbYellow);

       this.btg.add(this.jrbGreen);

       setLayout(new BorderLayout());

       add(p1, "Center");

       add(p2, "South");

       this.jrbRed.addItemListener(this);

       this.jrbYellow.addItemListener(this);

       this.jrbGreen.addItemListener(this);

   }

   public void itemStateChanged(ItemEvent e){

       if (this.jrbRed.isSelected()) {

           this.light.turnOnRed();

       }

       if (this.jrbYellow.isSelected()) {

           this.light.turnOnYellow();

       }

       if (this.jrbGreen.isSelected())

           this.light.turnOnGreen();

   }

   class Light extends JPanel{

       /**

       *

       */

       private static final long serialVersionUID = 1L;

       private boolean red;

       private boolean yellow;

       private boolean green;

       public void turnOnRed() {

           this.red = true;

           this.yellow = false;

           this.green = false;

           repaint();

       }

     

       public void turnOnYellow(){

           this.red = false;

           this.yellow = true;

           this.green = false;

           repaint();

     

       }

     

       public void turnOnGreen(){

           this.red = false;

           this.yellow = false;

           this.green = true;

           repaint();

       }

       protected void paintComponent(Graphics g){

           super.paintComponent(g);

           if (this.red) {

               g.setColor(Color.red);

               g.fillOval(10, 10, 20, 20);

               g.setColor(Color.black);

               g.drawOval(10, 35, 20, 20);

               g.drawOval(10, 60, 20, 20);

               g.drawRect(5, 5, 30, 80);

           }

         

           else if (this.yellow) {

               g.setColor(Color.yellow);

               g.fillOval(10, 35, 20, 20);

               g.setColor(Color.black);

               g.drawRect(5, 5, 30, 80);

               g.drawOval(10, 10, 20, 20);

               g.drawOval(10, 60, 20, 20);

           }

           else if (this.green) {

               g.setColor(Color.green);

               g.fillOval(10, 60, 20, 20);

               g.setColor(Color.black);

               g.drawRect(5, 5, 30, 80);

               g.drawOval(10, 10, 20, 20);

               g.drawOval(10, 35, 20, 20);

           }

           else {

               g.setColor(Color.black);

               g.drawRect(5, 5, 30, 80);

               g.drawOval(10, 10, 20, 20);

               g.drawOval(10, 35, 20, 20);

               g.drawOval(10, 60, 20, 20);

           }

       }

       public Dimension getPreferredSize(){

           return new Dimension(40, 90);

       }

   }

   public void actionPerformed(ActionEvent arg0) {

       // TODO Auto-generated method stub

   }

}

Outputs:

Traffic Li.. Red Yellow Green X OOO

Traffic Lig... Green Red OYellow X