JAVA NULLexception errors

[Jishnu]

Hi guys.I am creating a project in Netbeans JAVA for my school.Its sort of a Virtual Car Showroom.

I have Java-Mysql connectivity.

I am having certainly EXCEPTIONAL Nullexception errors.
Actually it's a sort of weird

Here's the error:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at JCS.VariantListValueChanged(JCS.java:2639)
at JCS.access$3200(JCS.java:22)
at JCS$33.valueChanged(JCS.java:1036)
at javax.swing.JList.fireSelectionValueChanged(JList. java:1798)
at javax.swing.JList$ListSelectionHandler.valueChange d(JList.java:1812)
at javax.swing.DefaultListSelectionModel.fireValueCha nged(DefaultListSelectionModel.java:184)
at javax.swing.DefaultListSelectionModel.fireValueCha nged(DefaultListSelectionModel.java:164)
at javax.swing.DefaultListSelectionModel.fireValueCha nged(DefaultListSelectionModel.java:211)
at javax.swing.DefaultListSelectionModel.removeIndexI nterval(DefaultListSelectionModel.java:677)
at javax.swing.plaf.basic.BasicListUI$Handler.interva lRemoved(BasicListUI.java:2601)
at javax.swing.AbstractListModel.fireIntervalRemoved( AbstractListModel.java:179)
at javax.swing.DefaultListModel.removeAllElements(Def aultListModel.java:404)
at JCS.ClearAll(JCS.java:2864)
at JCS.A4LblMouseClicked(JCS.java:2584)
at JCS.access$1300(JCS.java:22)
at JCS$14.mouseClicked(JCS.java:653)
at java.awt.AWTEventMulticaster.mouseClicked(AWTEvent Multicaster.java:270)
at java.awt.Component.processMouseEvent(Component.jav a:6507)
at javax.swing.JComponent.processMouseEvent(JComponen t.java:3321)
at java.awt.Component.processEvent(Component.java:626 9)
at java.awt.Container.processEvent(Container.java:222 9)
at java.awt.Component.dispatchEventImpl(Component.jav a:4860)
at java.awt.Container.dispatchEventImpl(Container.jav a:2287)
at java.awt.Component.dispatchEvent(Component.java:46 86)
at java.awt.LightweightDispatcher.retargetMouseEvent( Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(C ontainer.java:4501)
at java.awt.LightweightDispatcher.dispatchEvent(Conta iner.java:4422)
at java.awt.Container.dispatchEventImpl(Container.jav a:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2713 )
at java.awt.Component.dispatchEvent(Component.java:46 86)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.j ava:707)
at java.awt.EventQueue.access$000(EventQueue.java:101 )
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:680)
at java.awt.EventQueue$4.run(EventQueue.java:678)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java: 677)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:90)


I shall giv the links to my NETBEANS Project folder if u want it.
Time's goin......

Sorry guys.

I SOLVED it.

Everytime I clear List and Combobox, valuechanged() and ItemStateChanged()
Events were generated and since selected ITEM was null,there was an error.

for this,in valuechanged() event type:
if(evt.getValueIsAdjusting==true){
...}

In ItemStateChanged() type:
if(<evt.getStateChange()==evt.SELECTED){ //For Selection
...}