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
index = -1;
				} else{
					while(lastInsertion < items.length && internalCompare(comparator,parentPath,element,items[lastInsertion].getData()) == 0){
						
						
						if (items[lastInsertion].getData().equals(element)) {
							
							refresh(element);
							newItem = false;
						}
						lastInsertion ++;
					}
					
					if(lastInsertion == items.length) {
						index = -1;
					} else {
						index = lastInsertion + i; 					
					}
				}
			}
			if(newItem) {
				createTreeItem(widget, element, index);
			}		
		}
    }
	
    /**
     * See if element is the data of one of the elements in 
     * items.
     * @param items