Bug 127861 [DataBinding] Mark API provisional
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/updatables/UnionSet.java
/**
	 * Set of ISetWithListeners
	 */
	private HashSet childSets = new HashSet();
	
	/**
	 * Map of elements onto Integer reference counts. This map is constructed
	 * when the first listener is added to the union set. Null if nobody is 
	 * listening to the UnionSet.
	 */
	private HashMap refCounts = null;
	private IChangeListener childListener = new IChangeListener() {
		public void handleChange(ChangeEvent changeEvent) {
			switch (changeEvent.getChangeType()) {
			case ChangeEvent.ADD_MANY:
				processAdds((Collection)changeEvent.getNewValue());
				break;
				
			case ChangeEvent.REMOVE_MANY:
				processRemoves((Collection)changeEvent.getNewValue());
				break;
				
			case ChangeEvent.STALE:
				processStale(((Boolean)changeEvent.getNewValue()).booleanValue());