Thread: Problem with ItemListener.... help pleas

My problem is with ItemListener I'm not sure why it is not working. Well I'm trying to split the ItemListener
into two class.

in the main class I have this

final JCheckBox whole_C_CheckBox = new JCheckBox("Whole");
whole_C_CheckBox.addItemListener(new CheckBox(whole_C_QTextField, whole_C_WTextField, whole_C_PTextField));
whole_C_CheckBox.setVerticalAlignment(SwingConstants.BOTTOM);
whole_C_CheckBox.setHorizontalAlignment(SwingConstants.LEFT);
whole_C_CheckBox.setBounds(12, 66, 113, 25);
chikenPanel.add(whole_C_CheckBox);

In the other class I have

 
public class CheckBox implements ItemListener{
 
 
 
	private JTextField q;
	private JTextField p;
	private JTextField w;
	private JCheckBox whole_C_CheckBox;
 
	public CheckBox(JTextField whole_C_QTextField, JTextField whole_C_WTextField, JTextField whole_C_PTextField) {
 
		this.q = whole_C_QTextField;
		this.w = whole_C_WTextField;
		this.p = whole_C_PTextField;
 
 
	}
	@Override
	public void itemStateChanged(ItemEvent e) {
 
		if(whole_C_CheckBox.isSelected()){
 
			q.setText("");
			w.setText("");
			p.setText("");
 
		}
	       else{
 
			q.setText("0");
			w.setText("0.00");
			p.setText("0.00");
		}	
 
 
}}

will when I try to run the program its working.However, when I click on the Check Box for (whole_C_CheckBox ) it give an error I don't know what is wrong with my code.

Note: in the main class all these whole_C_QTextField, whole_C_WTextField, whole_C_PTextField has
been set in default to (0, 0.00, 0.00), so I'm trying when I click on Check Box for (whole_C_CheckBox )
it will set them to nothing, and if I unchecked them again they will return to their default (0, 0.00, 0.00).

This is the error I get:

 
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at test1.CheckBox.itemStateChanged(CheckBox.java:31)
	at javax.swing.AbstractButton.fireItemStateChanged(Unknown Source)
	at javax.swing.AbstractButton$Handler.itemStateChanged(Unknown Source)
	at javax.swing.DefaultButtonModel.fireItemStateChanged(Unknown Source)
	at javax.swing.JToggleButton$ToggleButtonModel.setSelected(Unknown Source)
	at javax.swing.JToggleButton$ToggleButtonModel.setPressed(Unknown Source)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
	at java.awt.Component.processMouseEvent(Unknown Source)
	at javax.swing.JComponent.processMouseEvent(Unknown Source)
	at java.awt.Component.processEvent(Unknown Source)
	at java.awt.Container.processEvent(Unknown Source)
	at java.awt.Component.dispatchEventImpl(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
	at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
	at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
	at java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.awt.Window.dispatchEventImpl(Unknown Source)
	at java.awt.Component.dispatchEvent(Unknown Source)
	at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.awt.EventQueue.access$200(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.awt.EventQueue$3.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue$4.run(Unknown Source)
	at java.awt.EventQueue$4.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)

I looked at line 31, but I can not find what is wrong.

Note: this is the line 31: if(whole_C_CheckBox.isSelected()){...etc