public void testisEmptyLeafCard() throws Exception {

		for (int i = 0; i < 100; i++) {

			RBtree empt = empty();
			if ((!empt.isEmpty()) && (empt.cardinality() == 0)) {
				throw new Exception("A NON-EMPTY TREE HAS ZERO CARDINALITY");
			}

			if(empt.isEmpty() && (empt.cardinality() != 0)) {
				throw new Exception("AN EMPTY TREE HAS A CARDINALITY");
			}
			emptyLeafTestCard++;
		}
	}