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/AbstractTreeViewer.java
tree.setRedraw(true);
	}
	/**
	 * Creates a new item.
	 * 
	 * @param parent
	 *           the parent widget
	 * @param style
	 *           SWT style bits
	 * @param index
	 *           if non-negative, indicates the position to insert the item
	 *           into its parent
	 * @return the newly-created item
	 */
	protected abstract Item newItem(Widget parent, int style, int index);
	/**
	 * Removes the given elements from this viewer. The selection is updated if
	 * required.
	 * <p>
	 * This method should be called (by the content provider) when elements
	 * have been removed from the model, in order to cause the viewer to
	 * accurately reflect the model. This method only affects the viewer, not
	 * the model.
	 * </p>
	 * 
	 * @param elements
	 *           the elements to remove
	 */
	public void remove(final Object[] elements) {
		assertElementsNotNull(elements);