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
TreePath parentPath = internalGetSorterParentPath(widget, comparator);
		Item[] items = getChildren(widget);
		
		 
		
		int lastInsertion = 0;		
		
		
		if(items.length == 0){
			for (int i = 0; i < elements.length; i++) {
				createTreeItem(widget, elements[i], -1);		
			}
			return;
		}
	
		for (int i = 0; i < elements.length; i++) {
			boolean newItem = true;
			Object element = elements[i];
			int index;
			if(comparator == null){
				if(itemExists(items,element)){
					refresh(element);
					newItem = false;
				}
				index = -1;
			}
			else{
				lastInsertion = insertionPosition(items,comparator,lastInsertion, element, parentPath);
				
				if(lastInsertion == items.length) {