public void buildTrie(Set<String> col) {
			for (String str : col) {
				Trie[] trieArray = sons;
				for (int i = 0; i < str.length(); ++i) {
					Trie tmpTrie;
					if (trieArray[str.charAt(i) - 'a'] == null) {
						tmpTrie = new Trie();
						tmpTrie.ch = str.charAt(i);
						trieArray[str.charAt(i) - 'a'] = tmpTrie;
					}
					tmpTrie = trieArray[str.charAt(i) - 'a'];
					if (i == str.length() - 1) {
						tmpTrie.finish = true;
					}
					trieArray = tmpTrie.sons;
				}
			}
			return;
		}