java.lang.NullPointerException
        at org.netbeans.modules.java.editor.codegen.ImplementOverrideMethodGenerator$1.run(ImplementOverrideMethodGenerator.java:156)
        at org.netbeans.modules.java.editor.codegen.ImplementOverrideMethodGenerator$1.run(ImplementOverrideMethodGenerator.java:152)
        at org.netbeans.api.java.source.JavaSource.runModificationTask(JavaSource.java:915)
        at org.netbeans.modules.java.editor.codegen.ImplementOverrideMethodGenerator.invoke(ImplementOverrideMethodGenerator.java:151)
        at org.netbeans.modules.java.editor.codegen.ui.GenerateCodePanel.invokeSelected(GenerateCodePanel.java:149)
        at org.netbeans.modules.java.editor.codegen.ui.GenerateCodePanel.listMouseReleased(GenerateCodePanel.java:118)
        at org.netbeans.modules.java.editor.codegen.ui.GenerateCodePanel.access$100(GenerateCodePanel.java:61)
        at org.netbeans.modules.java.editor.codegen.ui.GenerateCodePanel$2.mouseReleased(GenerateCodePanel.java:104)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:273)
        at java.awt.Component.processMouseEvent(Component.java:6134)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at java.awt.Component.processEvent(Component.java:5899)
        at java.awt.Container.processEvent(Container.java:2023)
        at java.awt.Component.dispatchEventImpl(Component.java:4501)
        at java.awt.Container.dispatchEventImpl(Container.java:2081)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4301)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:3965)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:3895)
        at java.awt.Container.dispatchEventImpl(Container.java:2067)
        at java.awt.Window.dispatchEventImpl(Window.java:2458)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        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)