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$ThreadReference$Status.enqueueCommand(JDWP.java:5089)
        at com.sun.tools.jdi.JDWP$ThreadReference$Status.process(JDWP.java:5075)
        at com.sun.tools.jdi.ThreadReferenceImpl.jdwpStatus(ThreadReferenceImpl.java:185)
        at com.sun.tools.jdi.ThreadReferenceImpl.isSuspended(ThreadReferenceImpl.java:201)
        at org.netbeans.modules.debugger.jpda.JPDAStepImpl$SingleThreadedStepWatch.run(JPDAStepImpl.java:657)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:561)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:986)