public void addWord (String word) {
		if (word == null || word.length() == 0) {
			return;
		}
		TrieTree curNode = this;
		int pos;
		char c;
		for (int i = 0; i < word.length(); i++) {
			c = word.charAt(i);
			pos = c - 'a';
			if (curNode.child[pos] == null) {
				curNode.child[pos] = new TrieTree(c);				
			}
			if (i == word.length() - 1) {
				curNode.child[pos].isWord = true;
				break;
			}
			curNode = curNode.child[pos];
		}
	}