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
protected void internalRemove(Object[] elementsOrPaths) {
        Object input = getInput();
        
        
        CustomHashtable parentItems = new CustomHashtable(5);
        for (int i = 0; i < elementsOrPaths.length; ++i) {
            Object element = elementsOrPaths[i];
			if (equals(element, input)) {
                setInput(null);
                return;
            }
            Widget[] childItems = internalFindItems(element);
			for (int j = 0; j < childItems.length; j++) {
				Widget childItem = childItems[j];
				if (childItem instanceof Item) {
					Item parentItem = getParentItem((Item) childItem);
					if (parentItem != null) {
						parentItems.put(parentItem, parentItem);
					}
					disassociate((Item) childItem);
					childItem.dispose();
				}
			}            
        }
        internalReconcileParentItems(parentItems);
    }
	/**
	 * @param parentItems
	 */
	private void internalReconcileParentItems(CustomHashtable parentItems) {