Java Made Simple: Create Checkbox Example

Checkbox Example tutorial is given in Question/Answer format for easy understanding.

1. What is Checkbox?

Checkbox is one of the GUI components Java supports.

2. When Checkbox is preferred by the Programmer?

Checkbox is used when the user has got only two options to choose in between like Yes or No, Want or Dont want.

3. How to create a Checkbox component?

Checkbox cb1 = new Checkbox("Hero Honda"); OR
Checkbox cb2 = new Checkbox("Hero Honda", true);

cb1 displays a checkbox with label Hero Honda; here, the checkbox is NOT SELECTED by default.
cb2 displays a checkbox with label Hero Honda; here, the checkbox is SELECTED by default which user can change.

4. How to know which checkbox is selected by user?

The getState() method of Checkbox class returns true if the user selected the checkbox else false.

boolean b = cb1.getState();
System.out.println(b);

b prints true if user selects (or checks) the checkbox cb1, else b prints false.

5. Which event is generated by Checkbox?

When user selects a checkbox, the checkbox generates an event known as ItemEvent (from java.awt.event package).

6. What is the listener interface that handles the ItemEvent successfully?

ItemListener (from java.awt.event package) is capable to handle the event ItemEvent.

7. Can we use checkboxes in applets also?

Yes; infact you can use any GUI component in applets (apart in frame) also. But menus cannot be done in applets.

To get the concept, a simple program is given explaining how to use checkboxes. A big program, we see later.

Checkbox Example: Just two checkboxes are created and added to frame with labels Hero Honda and Activa. For simplicity, user selection is displayed at DOS prompt.

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

public class WhatYouWant extends Frame implements ItemListener
{
  Checkbox hondaBox, activaBox;		        // reference variables
  public WhatYouWant()
  {    					        // set the layout first  
    setLayout(new FlowLayout());
					        // convert reference variables into objects
    hondaBox = new Checkbox("Hero Honda");	// Hero Honda is not selected by default
    activaBox = new Checkbox("Activa", true);	// Activa  is selected by default
			
   hondaBox.addItemListener(this);		// link with ItemListener
   activaBox.addItemListener(this);
   
    add(hondaBox);   add(activaBox);		// add checkboxes to frame to display

    setTitle("Simple Checkbox Program");	// set methods of frame
    setSize(300, 200);
    setVisible(true);
  }
  public void itemStateChanged(ItemEvent e)
  {
    boolean b1 = hondaBox.getState();		// b1 is true if hondaBox is selected. else false
    boolean b2 = activaBox.getState();		// b2 is true if activaBox is selected. else false

    System.out.println("You wanted Hero Honda: " + b1);
    System.out.println("You wanted Activa: " + b2 + "\n");
  }
  public static void main(String args[])
  {
    new WhatYouWant();			        // create anonymous object just to call the constructor
  }
}

Output screenshot with different options selected. Observe, the last option and the screen.

A big and different program with full explanation and screenshot is available at Java AWT Checkbox – Toggle Button