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/CheckboxTableViewer.java
Widget widget = findItem(element);
	if (widget instanceof TableItem) {
		((TableItem) widget).setChecked(state);
		return true;
	}
	return false;
}
/**
 * Sets which nodes are checked in this viewer.
 * The given list contains the elements that are to be checked;
 * all other nodes are to be unchecked.
 * <p>
 * This method is typically used when restoring the interesting
 * state of a viewer captured by an earlier call to <code>getCheckedElements</code>.
 * </p>
 *
 * @param elements the list of checked elements (element type: <code>Object</code>)
 * @see #getCheckedElements
 */
public void setCheckedElements(Object[] elements) {
	assertElementsNotNull(elements);
	Set set = new HashSet(elements.length*2+1);
	for (int i = 0; i < elements.length; ++i) {
		set.add(elements[i]);
	}
	TableItem[] items = getTable().getItems();
	for (int i = 0; i < items.length; ++i) {
		TableItem item = items[i];
		Object element = item.getData();
		if (element != null) {