Bug 81070 ElementMapper should not use Integer keys computed from System#identityHashCode
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/workingsets/WorkingSetModel.java
addToMap(fElementToWorkingSet, element, ws);
			IResource resource= (IResource)element.getAdapter(IResource.class);
			if (resource != null) {
				addToMap(fResourceToWorkingSet, resource, ws);
			}
		}
		private void removeElement(IAdaptable element, IWorkingSet ws) {
			removeFromMap(fElementToWorkingSet, element, ws);
			IResource resource= (IResource)element.getAdapter(IResource.class);
			if (resource != null) {
				removeFromMap(fResourceToWorkingSet, resource, ws);
			}
		}
		private void addToMap(Map map, IAdaptable key, IWorkingSet value) {
			Object obj= map.get(key);
			if (obj == null) {
				map.put(key, value);
			} else if (obj instanceof IWorkingSet) {
				List l= new ArrayList(2);
				l.add(obj);
				l.add(value);
				map.put(key, l);
			} else if (obj instanceof List) {
				((List)obj).add(value);
			}
		}
		private void removeFromMap(Map map, IAdaptable key, IWorkingSet value) {
			Object current= map.get(key);
			if (current == null) {
				return;