Bug 138608 [Viewers] JFace AbstractTreeViewer: itemExists doesn't handle equal tree entries
I use a TreeViewer with - setUseHashLookup(true) - without any sorter or filter - with a comparer When I try to add an object that is equal to an existing entry in the tree, it will not be added. This is because the method private boolean itemExists(Item[] items, Object element) { if(usingElementMap()) { return findItem(element) != null; } for (int i = 0; i < items.length; i++) { if(items[i].getData().equals(element)) { return true; } } return false; } takes a shortcut if there is an element map, but the shortcut doesn't handle the 'multiple equal elements' case. There is a workaround, however: Setting a dummy sorter will avoid the call to itemExists and multiple equal elements can be added to the tree.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* viewer captured by an earlier call to <code>getExpandedTreePaths</code>.
     * </p>
     * 
     * @param treePaths
     *           the array of expanded tree paths
     * @see #getExpandedTreePaths()
     * 
     * @since 3.2
     */
    public void setExpandedTreePaths(TreePath[] treePaths) {
        assertElementsNotNull(treePaths);
        final IElementComparer comparer = getComparer();
        IElementComparer treePathComparer = new IElementComparer(){
			public boolean equals(Object a, Object b) {
				return ((TreePath)a).equals(((TreePath)b), comparer);
			}
			public int hashCode(Object element) {
				return ((TreePath)element).hashCode(comparer);
			}};
        CustomHashtable expandedTreePaths = new CustomHashtable(treePaths.length * 2 + 1, treePathComparer);
        for (int i = 0; i < treePaths.length; ++i) {
            TreePath treePath = treePaths[i];
            
            
            
            
            internalExpand(treePath, false);
            expandedTreePaths.put(treePath, treePath);
        }