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
}
        }
        Control tree = getControl();
        
        int oldCnt = -1;
        if (widget == tree) {
			oldCnt = getItemCount(tree);
		}
        Item[] items = getChildren(widget);
        
        CustomHashtable expanded = newHashtable(CustomHashtable.DEFAULT_CAPACITY); 
        for (int i = 0; i < items.length; ++i) {
            if (getExpanded(items[i])) {
                Object element = items[i].getData();
                if (element != null) {
                    expanded.put(element, element);
                }
            }
        }
        int min = Math.min(elementChildren.length, items.length);
        
        
        
        
        
        for (int i = items.length; --i >= min;) {
            if (items[i].getData() != null) {
                disassociate(items[i]);
            }
            items[i].dispose();