when i run my application i get the following error:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javax.swing.text.FlowView$FlowStrategy.layoutRow(FlowView.java:546)
    at javax.swing.text.FlowView$FlowStrategy.layout(FlowView.java:460)
    at javax.swing.text.FlowView.layout(FlowView.java:184)
    at javax.swing.text.BoxView.setSize(BoxView.java:380)
    at javax.swing.text.BoxView.updateChildSizes(BoxView.java:349)
    at javax.swing.text.BoxView.setSpanOnAxis(BoxView.java:331)
    at javax.swing.text.BoxView.layout(BoxView.java:691)
    at javax.swing.text.BoxView.setSize(BoxView.java:380)
    at javax.swing.plaf.basic.BasicTextUI$RootView.setSize(BasicTextUI.java:1702)
    at javax.swing.plaf.basic.BasicTextUI.modelToView(BasicTextUI.java:1034)
    at javax.swing.text.DefaultCaret.repaintNewCaret(DefaultCaret.java:1291)
    at javax.swing.text.DefaultCaret$1.run(DefaultCaret.java:1270)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

as the error does not mention any of my classes, how would i go about in finding what is causing this?

if i try: public void notifyChatMessage(String message){...} the error goes away.

but if i try: public void notifyChatMessage(Object message){...} the error is reported.

please advise.