Bug 258736 [Viewers] [JFace] setUseHashLookUp() and multiple occurrences of same domain object in TreeViewer
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java
/**
	 * Creates a tree viewer on a newly-created tree control under the given
	 * parent. The tree control is created using the given SWT style bits. The
	 * viewer has no input, no content provider, a default label provider, no
	 * sorter, and no filters.
	 *
	 * @param parent
	 *            the parent control
	 * @param style
	 *            the SWT style bits used to create the tree.
	 */
	public TreeViewer(Composite parent, int style) {
		this(new Tree(parent, style));
	}
	/**
	 * Creates a tree viewer on the given tree control. The viewer has no input,
	 * no content provider, a default label provider, no sorter, and no filters.
	 *
	 * @param tree
	 *            the tree control
	 */
	public TreeViewer(Tree tree) {
		super();
		this.tree = tree;
		hookControl(tree);
	}
	/*
	 * (non-Javadoc) Method declared in AbstractTreeViewer.
	 */
	protected void addTreeListener(Control c, TreeListener listener) {