// Demonstrate 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 checkboxes 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 what 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();  
      }  
    });  
  }  
}