Bug 32254 [Viewers] AbstractTreeViewer uses HashSet to remember expansion state
I20030216 The custom hash table should be used instead. Otherwise expansion state may be lost due to a different equals implementation of the element and the IElementComparer.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/CheckboxTreeViewer.java
* @param widget the widget
 */
private void applyState(Set checked, Set grayed, Widget widget) {
	Item[] items = getChildren(widget);
	for (int i = 0; i < items.length; i++) {
		Item item = items[i];
		if (item instanceof TreeItem) {
			Object data = item.getData();
			if (data != null) {
				TreeItem ti = (TreeItem) item;
				ti.setChecked(checked.contains(data));
				ti.setGrayed(grayed.contains(data));
			}
		}
		applyState(checked, grayed, item);
	}
}
/**
 * Notifies any check state listeners that the check state of an element has changed.
 * Only listeners registered at the time this method is called are notified.
 *
 * @param event a check state changed event
 *
 * @see ICheckStateListener#checkStateChanged
 */
protected void fireCheckStateChanged(final CheckStateChangedEvent event) {
	Object[] array = checkStateListeners.getListeners();
	for (int i = 0; i < array.length; i ++) {
		final ICheckStateListener l = (ICheckStateListener)array[i];
		Platform.run(new SafeRunnable() {