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
* 
     */
	
	private int insertionPosition(Item[] items,  ViewerComparator comparator, int lastInsertion, Object element, TreePath parentPath) {
		
		int size = items.length;
		if (comparator == null) {
			return size;
		}
	    int min = lastInsertion, max = size - 1;
		while (min <= max) {
            int mid = (min + max) / 2;
            Object data = items[mid].getData();
            int compare = internalCompare(comparator, parentPath, data, element);
            if (compare == 0) {
                return mid;
            }
            if (compare < 0) {
				min = mid + 1;
			} else {
				max = mid - 1;
			}
	        }
	   return min;
	    
			
	}
	/**
     * Returns the index where the item should be inserted. It uses sorter to
     * determine the correct position, if sorter is not assigned, returns the