Working with check boxes in java!

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// Demostrate check boxes.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class CBDemo implements ItemListener {
 JLabel jlabSelected;
 JLabel jlabChanged;
 JCheckBox jcbAlpha;
 JCheckBox jcbBeta;
 JCheckBox jcbGamma;

 CBDemo () {
  // Create a new JFrame container.
  JFrame jfrm = new JFrame("Demonstrate Check Boxes");

  // Specify FlowLayout for the layout manager.
  jfrm.setLayout (new FlowLayout());

  // Give the frame an initial size.
  jfrm.setSize(280, 120);

  // Terminate the program when the user closes the application.
  jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  // Create empty labels. 
  jlabSelected = new JLabel("");
  jlabChanged = new JLabel("");

  // Make check boxes.
  jcbAlpha = new JCheckBox("Alpha");
  jcbBeta = new JCheckBox("Beta");
  jcbGamma = new JCheckBox("Gamma");

  // Events generated by the check boxes
  // are handled in common by the itemStateChanged()
  // method implemented by CBDemo.
  jcbAlpha.addItemListener(this);
  jcbBeta.addItemListener(this);
  jcbGamma.addItemListener(this);

  // add check boxes and labels to the content pane.
  jfrm.add(jcbAlpha);
  jfrm.add(jcbBeta);
  jfrm.add(jcbGamma);
  jfrm.add(jlabChanged);
  jfrm.add(jlabSelected);

  // Display the frame.
  jfrm.setVisible(true);
 }

 // This is the handler for the check boxes.
 public void itemStateChanged(ItemEvent ie) {
  String str = "";
  
  // obtain a reference to the check box that 
  // caused the event.
  JCheckBox cb = (JCheckBox) ie.getItem();

  // report that check box changed.
  if(cb.isSelected())
   jlabChanged.setText(cb.getText() + " was just selected.");
  else
   jlabChanged.setText(cb.getText() + " was just cleared.");

  // report all selected boxes.
  if(jcbAlpha.isSelected()) {
   str += "Alpha ";
  }
  if(jcbBeta.isSelected()) {
   str += "Beta ";
  }
  if(jcbGamma.isSelected()) {
   str += "Gamma ";
  }
  
  jlabSelected.setText("Selected check boxes: " + str);
 }

 public static void main(String args[]) {
  // create the frame on the event dispatching thread.
  SwingUtilities.invokeLater(new Runnable() {
   public void run() {
    new CBDemo();
   }
  });
 }
}