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
}
	    	tpvs.sort(this, path, result);
		} else if (comparator != null) {
			
			result = (Object[]) result.clone();
			comparator.sort(this, result);
		}
		return result;
	}
	
	/* (non-Javadoc)
	 * @see org.eclipse.jface.viewers.StructuredViewer#getFilteredChildren(java.lang.Object)
	 */
	protected Object[] getFilteredChildren(Object parentElementOrTreePath) {
		Object[] result = getRawChildren(parentElementOrTreePath);
		ViewerFilter[] filters = getFilters();
		for (int i = 0; i < filters.length; i++) {
			ViewerFilter filter = filters[i];
			result = filter.filter(this, parentElementOrTreePath, result);
		}
		return result;
	}
	
    /**
     * Adds the given child element to this viewer as a child of the given
     * parent element. If this viewer does not have a sorter, the element is
     * added at the end of the parent's list of children; otherwise, the
     * element is inserted at the appropriate position.
     * <p>
     * This method should be called (by the content provider) when a single