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
toRemove.put(elements[i], elements[i]);
		}
        
        
        CustomHashtable parentItems = new CustomHashtable(5);
        
    	Widget[] parentItemArray = findItems(parent);
        for (int i = 0; i < parentItemArray.length; i++) {
        	Widget parentItem = parentItemArray[i];
        	
        	if (parentItem instanceof Item) {
        		parentItems.put(parentItem, parentItem);
        	}
        	
        	
        	Item[] children = getChildren(parentItem);
        	
        	for (int j = 0; j < children.length; j++) {
				Item child = children[j];
				
		        Object data = child.getData();
		        if (data !=null && toRemove.containsKey(data)) {
					disassociate(child);
					child.dispose();
		        }
			}            	
		}            
        internalReconcileParentItems(parentItems);
    }
    /**