private void insert(Comparable key, Node currentNode) {
		if(currentNode != null) {
			if(key.compareTo(currentNode.key) < 0) {
				if(currentNode.left != null) {
					insert(key, currentNode.left);
				} else {
					currentNode.left = new Node(key);
				}
			} else if(key.compareTo(currentNode.key) > 0) {
				if(currentNode.right != null) {
					insert(key, currentNode.right);
				} else {
					currentNode.right = new Node(key);
				}
			}				
		} else {
			currentNode = new Node(key);
		}
	}