com.sun.jdi.VMDisconnectedException: connection is closed
        at com.sun.tools.jdi.TargetVM.send(TargetVM.java:274)
        at com.sun.tools.jdi.VirtualMachineImpl.sendToTarget(VirtualMachineImpl.java:1011)
        at com.sun.tools.jdi.PacketStream.send(PacketStream.java:41)
        at com.sun.tools.jdi.JDWP$ThreadReference$FrameCount.enqueueCommand(JDWP.java:5300)
        at com.sun.tools.jdi.JDWP$ThreadReference$FrameCount.process(JDWP.java:5286)
        at com.sun.tools.jdi.ThreadReferenceImpl.frameCount(ThreadReferenceImpl.java:254)
        at org.netbeans.modules.debugger.jpda.models.JPDAThreadImpl.getStackDepth(JPDAThreadImpl.java:512)
        at org.netbeans.modules.debugger.jpda.models.JPDAThreadImpl.getCallStack(JPDAThreadImpl.java:382)
        at org.netbeans.modules.debugger.jpda.ui.models.DebuggingTreeModel.computeChildren(DebuggingTreeModel.java:140)
        at org.netbeans.modules.debugger.jpda.ui.models.CachedChildrenTreeModel.getChildren(CachedChildrenTreeModel.java:74)
        at org.netbeans.spi.viewmodel.Models$DelegatingTreeModel.getChildren(Models.java:1198)
        at org.netbeans.modules.debugger.jpda.ui.models.DebuggingMonitorModel.getChildren(DebuggingMonitorModel.java:199)
        at org.netbeans.spi.viewmodel.Models$CompoundTreeModel.getChildren(Models.java:678)
        at org.netbeans.modules.debugger.jpda.ui.models.HiddenCallStackFramesFilter.getChildren(HiddenCallStackFramesFilter.java:227)
        at org.netbeans.spi.viewmodel.Models$CompoundTreeModel.getChildren(Models.java:678)
        at org.netbeans.spi.viewmodel.Models$CompoundModel.getChildren(Models.java:2971)
        at org.netbeans.modules.viewmodel.TreeModelNode$TreeModelChildren.evaluateLazily(TreeModelNode.java:750)
        at org.netbeans.modules.viewmodel.TreeModelNode$LazyEvaluator.run(TreeModelNode.java:1177)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:572)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:997)