java.lang.NullPointerException
        at org.netbeans.modules.java.source.classpath.CacheClassPath.<init>(CacheClassPath.java:85)
        at org.netbeans.modules.java.source.classpath.CacheClassPath.forClassPath(CacheClassPath.java:192)
        at org.netbeans.api.java.source.ClasspathInfo.<init>(ClasspathInfo.java:112)
        at org.netbeans.api.java.source.ClasspathInfo.create(ClasspathInfo.java:192)
        at org.netbeans.modules.java.j2seproject.J2SEProjectUtil.isMainClass(J2SEProjectUtil.java:118)
        at org.netbeans.modules.java.j2seproject.J2SEActionProvider.isSetMainClass(J2SEActionProvider.java:900)
        at org.netbeans.modules.java.j2seproject.J2SEActionProvider.getTargetNames(J2SEActionProvider.java:436)
        at org.netbeans.modules.java.j2seproject.J2SEActionProvider$3.run(J2SEActionProvider.java:318)
        at org.netbeans.api.java.source.ui.ScanDialog.runWhenScanFinished(ScanDialog.java:150)
        at org.netbeans.modules.java.j2seproject.J2SEActionProvider.invokeAction(J2SEActionProvider.java:356)
        at org.netbeans.modules.project.ui.actions.MainProjectAction.actionPerformed(MainProjectAction.java:121)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
        at java.awt.Component.processMouseEvent(Component.java:6041)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at java.awt.Component.processEvent(Component.java:5806)
        at java.awt.Container.processEvent(Container.java:2058)
        at java.awt.Component.dispatchEventImpl(Component.java:4413)
        at java.awt.Container.dispatchEventImpl(Container.java:2116)
        at java.awt.Component.dispatchEvent(Component.java:4243)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4322)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:3986)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:3916)
        at java.awt.Container.dispatchEventImpl(Container.java:2102)
        at java.awt.Window.dispatchEventImpl(Window.java:2440)
        at java.awt.Component.dispatchEvent(Component.java:4243)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)