java.lang.IllegalStateException: Warning: multiple instances of shared class org.netbeans.modules.xml.actions.CollectDTDAction created.
        at org.openide.util.SharedClassObject.<init>(SharedClassObject.java:185)
        at org.openide.util.actions.SystemAction.<init>(SystemAction.java:84)
        at org.netbeans.modules.xml.actions.CollectSystemAction.<init>(CollectSystemAction.java:58)
        at org.netbeans.modules.xml.actions.CollectDTDAction.<init>(CollectDTDAction.java:56)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(NativeConstructorAccessorImpl.java:0)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at java.lang.Class.newInstance0(Class.java:355)
        at java.lang.Class.newInstance(Class.java:308)
        at org.netbeans.modules.xml.actions.CollectDTDAction.getInstance(CollectDTDAction.java:63)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:0)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.netbeans.core.startup.layers.BinaryFS$AttrImpl$MethodAndParams.invoke(BinaryFS.java:603)
        at org.netbeans.core.startup.layers.BinaryFS$AttrImpl.getValue(BinaryFS.java:536)
        at org.netbeans.core.startup.layers.BinaryFS$BFSBase.getAttribute(BinaryFS.java:382)
        at org.openide.filesystems.MultiFileObject.getAttribute(MultiFileObject.java:844)
        at org.openide.filesystems.MultiFileObject.getAttribute(MultiFileObject.java:793)
        at org.openide.filesystems.MultiFileObject.getAttribute(MultiFileObject.java:840)
        at org.openide.filesystems.MultiFileObject.getAttribute(MultiFileObject.java:793)
        at org.openide.filesystems.MultiFileObject.getAttribute(MultiFileObject.java:726)
        at org.netbeans.core.startup.layers.BinaryFS$FileMap.get(BinaryFS.java:959)
        at org.openide.awt.AlwaysEnabledAction.getDelegate(AlwaysEnabledAction.java:83)
        at org.openide.awt.AlwaysEnabledAction.actionPerformed(AlwaysEnabledAction.java:126)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.AbstractButton.doClick(AbstractButton.java:357)
        at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1223)
        at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:1264)
        at java.awt.Component.processMouseEvent(Component.java:6263)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3255)
        at java.awt.Component.processEvent(Component.java:6028)
        at java.awt.Container.processEvent(Container.java:2041)
        at java.awt.Component.dispatchEventImpl(Component.java:4630)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4574)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4238)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4168)
        at java.awt.Container.dispatchEventImpl(Container.java:2085)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:125)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)