java.lang.IllegalArgumentException: Invalid ClassPath root: file:/C:/Users/iwan/.netbeans/6.7beta/var/cache/index/s102/java/13/classes/. The root must be a folder.
        at org.netbeans.api.java.classpath.ClassPath$Entry.getRoot(ClassPath.java:691)
        at org.netbeans.api.java.classpath.ClassPath.createRoots(ClassPath.java:271)
        at org.netbeans.api.java.classpath.ClassPath.getRoots(ClassPath.java:252)
        at org.netbeans.api.java.classpath.ClassPath.findAllResources(ClassPath.java:381)
        at org.netbeans.api.java.source.SourceUtils.getFile(SourceUtils.java:398)
        at org.netbeans.api.java.source.SourceUtils.getFile(SourceUtils.java:361)
        at org.netbeans.modules.java.source.TreeLoader.loadTreeFor(TreeLoader.java:139)
        at com.sun.tools.javac.code.Symbol$ParamSymbol.getSimpleName(Symbol.java:1062)
        at com.sun.tools.javac.code.Symbol$ParamSymbol.getSimpleName(Symbol.java:1029)
        at org.netbeans.modules.java.editor.overridden.ElementDescription$ElementNameVisitor.visitVariable(ElementDescription.java:150)
        at org.netbeans.modules.java.editor.overridden.ElementDescription$ElementNameVisitor.visitVariable(ElementDescription.java:107)
        at com.sun.tools.javac.code.Symbol$VarSymbol.accept(Symbol.java:952)
        at org.netbeans.modules.java.editor.overridden.ElementDescription$ElementNameVisitor.visitExecutable(ElementDescription.java:140)
        at org.netbeans.modules.java.editor.overridden.ElementDescription$ElementNameVisitor.visitExecutable(ElementDescription.java:107)
        at com.sun.tools.javac.code.Symbol$MethodSymbol.accept(Symbol.java:1359)
        at org.netbeans.modules.java.editor.overridden.ElementDescription.<init>(ElementDescription.java:80)
        at org.netbeans.modules.java.editor.overridden.IsOverriddenAnnotationHandler.process(IsOverriddenAnnotationHandler.java:306)
        at org.netbeans.modules.java.editor.overridden.IsOverriddenAnnotationHandler.run(IsOverriddenAnnotationHandler.java:130)
        at org.netbeans.modules.java.editor.overridden.IsOverriddenAnnotationHandler.run(IsOverriddenAnnotationHandler.java:103)
        at org.netbeans.modules.java.source.JavaSourceAccessor$CancelableTaskWrapper.run(JavaSourceAccessor.java:288)
        at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:668)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:619)