java.util.ConcurrentModificationException: null
    at org.eclipse.emf.ecore.util.FeatureMapUtil$BasicFeatureEIterator.checkModCount(FeatureMapUtil.java:555)
    at org.eclipse.emf.ecore.util.FeatureMapUtil$BasicFeatureEIterator.next(FeatureMapUtil.java:373)
    at org.eclipse.jst.jee.model.internal.mergers.EjbJarMerger.mergeSessionBeans(EjbJarMerger.java:145)
    at org.eclipse.jst.jee.model.internal.mergers.EjbJarMerger.process(EjbJarMerger.java:74)
    at org.eclipse.jst.jee.model.internal.EJB3MergedModelProvider.mergeWithModel(EJB3MergedModelProvider.java:214)
    at org.eclipse.jst.jee.model.internal.EJB3MergedModelProvider.merge(EJB3MergedModelProvider.java:204)
    at org.eclipse.jst.jee.model.internal.EJB3MergedModelProvider.internalModelChanged(EJB3MergedModelProvider.java:174)
    at org.eclipse.jst.jee.model.internal.EJB3MergedModelProvider.annotationModelChanged(EJB3MergedModelProvider.java:151)
    at org.eclipse.jst.jee.model.internal.common.AbstractMergedModelProvider$AnnotationModelListener.modelsChanged(AbstractMergedModelProvider.java:83)
    at org.eclipse.jst.jee.model.internal.common.AbstractAnnotationModelProvider$1.run(AbstractAnnotationModelProvider.java:189)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.jst.jee.model.internal.common.AbstractAnnotationModelProvider.notifyListeners(AbstractAnnotationModelProvider.java:184)
    at org.eclipse.jst.jee.model.internal.common.AbstractAnnotationModelProvider.notifyListeners(AbstractAnnotationModelProvider.java:157)
    at org.eclipse.jst.jee.model.internal.common.AbstractAnnotationModelProvider.internalPostReconcile(AbstractAnnotationModelProvider.java:467)
    at org.eclipse.jst.jee.model.internal.common.AbstractAnnotationModelProvider.elementChanged(AbstractAnnotationModelProvider.java:446)
    at org.eclipse.jdt.internal.core.DeltaProcessor$3.run(DeltaProcessor.java:1662)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.jdt.internal.core.DeltaProcessor.notifyListeners(DeltaProcessor.java:1652)
    at org.eclipse.jdt.internal.core.DeltaProcessor.fireReconcileDelta(DeltaProcessor.java:1504)
    at org.eclipse.jdt.internal.core.DeltaProcessor.fire(DeltaProcessor.java:1463)
    at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:770)
    at org.eclipse.jdt.internal.core.JavaModelOperation.runOperation(JavaModelOperation.java:789)
    at org.eclipse.jdt.internal.core.CompilationUnit.reconcile(CompilationUnit.java:1250)
    at org.eclipse.jdt.internal.core.CompilationUnit.reconcile(CompilationUnit.java:1227)
    at org.eclipse.jdt.internal.core.CompilationUnit.reconcile(CompilationUnit.java:1192)
    at org.jboss.tools.websockets.ui.internal.ca.SocketProposalComputer.computeCompletionProposals(SocketProposalComputer.java:130)
    at org.eclipse.jdt.internal.ui.text.java.CompletionProposalComputerDescriptor.computeCompletionProposals(CompletionProposalComputerDescriptor.java:333)
    at org.eclipse.jdt.internal.ui.text.java.CompletionProposalCategory.computeCompletionProposals(CompletionProposalCategory.java:337)
    at org.eclipse.jdt.internal.ui.text.java.ContentAssistProcessor.collectProposals(ContentAssistProcessor.java:322)
    at org.eclipse.jdt.internal.ui.text.java.ContentAssistProcessor.computeCompletionProposals(ContentAssistProcessor.java:279)
    at org.eclipse.jface.text.contentassist.ContentAssistant$5.run(ContentAssistant.java:1904)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.jface.text.contentassist.ContentAssistant.computeCompletionProposals(ContentAssistant.java:1902)
    at org.eclipse.jface.text.contentassist.CompletionProposalPopup.computeProposals(CompletionProposalPopup.java:573)
    at org.eclipse.jface.text.contentassist.CompletionProposalPopup.access$16(CompletionProposalPopup.java:570)
    at org.eclipse.jface.text.contentassist.CompletionProposalPopup$2.run(CompletionProposalPopup.java:505)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
    at org.eclipse.jface.text.contentassist.CompletionProposalPopup.showProposals(CompletionProposalPopup.java:499)
    at org.eclipse.jface.text.contentassist.ContentAssistant.showPossibleCompletions(ContentAssistant.java:1720)
    at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor$AdaptedSourceViewer.doOperation(CompilationUnitEditor.java:180)
    at org.eclipse.ui.texteditor.ContentAssistAction$1.run(ContentAssistAction.java:82)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
    at org.eclipse.ui.texteditor.ContentAssistAction.run(ContentAssistAction.java:80)
    at org.eclipse.jface.action.Action.runWithEvent(Action.java:473)
    at org.eclipse.jface.commands.ActionHandler.execute(ActionHandler.java:122)
    at org.eclipse.ui.internal.handlers.E4HandlerProxy.execute(E4HandlerProxy.java:90)
    at sun.reflect.GeneratedMethodAccessor.invoke(null:-1)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(null:-1)
    at java.lang.reflect.Method.invoke(null:-1)
    at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:56)