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
if (expanded.contains(elementChildren[i])) {
						setExpanded(items[i], true);
					}
				}
			}
		}
		
		if (widget == tree && oldCnt == 0 && getItemCount(tree) != 0) {
			
			tree.setRedraw(false);
			tree.setRedraw(true);
		}
	}
	/**
	 * Updates the "+"/"-" icon of the tree node from the given element. It
	 * calls <code>isExpandable</code> to determine whether an element is
	 * expandable.
	 * 
	 * @param item
	 *           the item
	 * @param element
	 *           the element
	 */
	protected void updatePlus(Item item, Object element) {
		boolean hasPlus = getItemCount(item) > 0;
		boolean needsPlus = isExpandable(element);