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
Item[] siblings = getItems(parent);
        if (siblings != null){
        	if(siblings.length <= 1) {
				return getNextItem(parent, false);
			}
        	
        	for (int i = 0; i < siblings.length; i++) {
                if (siblings[i] == item && i < (siblings.length - 1)) {
                    return siblings[i + 1];
                }
            }
        }
        return getNextItem(parent, false);
    }
    /**
     * Returns the parent item of the given item in the tree, or <code>null</code>
     * if there is no parent item.
     * 
     * @param item
     *           the item
     * @return the parent item, or <code>null</code> if none
     */
    protected abstract Item getParentItem(Item item);
    /**
     * Returns the item before the given item in the tree, or <code>null</code>
     * if there is no previous item.
     * 
     * @param item
     *           the item
     * @return the previous item, or <code>null</code> if none