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
}
        }
        if (childElements.length > 0) {
        	
            Object[] filtered = filter(parentElementOrTreePath, childElements);
			ViewerComparator comparator = getComparator();
			if(comparator != null) {
				if (comparator instanceof TreePathViewerSorter) {
					TreePathViewerSorter tpvs = (TreePathViewerSorter) comparator;
					if (path == null) {
						path = internalGetSorterParentPath(widget, comparator);
					}
					tpvs.sort(this, path, filtered);
				} else {
					comparator.sort(this,filtered);
				}
			}
            createAddedElements(widget, filtered);
        }
	}
	/**
	 * Filter the children elements.
	 * @param parentElementOrTreePath the parent element or path
	 * @param elements the child elements
	 * @return the filter list of children
	 */
	private Object[] filter(Object parentElementOrTreePath, Object[] elements) {
		ViewerFilter[] filters = getFilters();
		if (filters != null) {
			ArrayList filtered = new ArrayList(elements.length);