java.lang.IllegalArgumentException: Invalid field
        at com.sun.tools.jdi.ReferenceTypeImpl.validateFieldAccess(ReferenceTypeImpl.java:608)
        at com.sun.tools.jdi.ObjectReferenceImpl.getValues(ObjectReferenceImpl.java:163)
        at com.sun.tools.jdi.ObjectReferenceImpl.getValue(ObjectReferenceImpl.java:148)
        at org.netbeans.modules.debugger.jpda.expr.EvaluatorVisitor.visitIdentifier(EvaluatorVisitor.java:1257)
        at org.netbeans.modules.debugger.jpda.expr.EvaluatorVisitor.visitIdentifier(EvaluatorVisitor.java:169)
        at com.sun.tools.javac.tree.JCTree$JCIdent.accept(JCTree.java:1689)
        at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:49)
        at org.netbeans.modules.debugger.jpda.projects.EditorContextImpl.parseExpression(EditorContextImpl.java:1570)
        at sun.reflect.GeneratedMethodAccessor148.invoke(GeneratedMethodAccessor148.java:0)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.netbeans.modules.debugger.jpda.EditorContextBridge.parseExpression(EditorContextBridge.java:128)
        at org.netbeans.modules.debugger.jpda.expr.TreeEvaluator.evaluate(TreeEvaluator.java:121)
        at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.evaluateIn(JPDADebuggerImpl.java:723)
        at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.evaluateIn(JPDADebuggerImpl.java:627)
        at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.evaluateIn(JPDADebuggerImpl.java:598)
        at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.evaluate(JPDADebuggerImpl.java:268)
        at org.netbeans.modules.debugger.jpda.projects.ToolTipAnnotation.run(ToolTipAnnotation.java:148)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:561)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:986)