docs: public void addWord(String word) {
  		WordTree parent = null;
  		WordTree current = this;
  		WordTree child;
  		char currentChar = 0;
  		int length = word.length();
  		for(int i = 0; i < length; i++){
  			currentChar = word.charAt(i);
  			if(false == StopChar.isStopChar(currentChar)){//只处理合法字符
  				child = current.get(currentChar);
  				if(child == null){
  					//无子类，新建一个子节点后存放下一个字符
  					child = new WordTree();
  					current.put(currentChar, child);
  				}
  				parent = current;
  				current = child;
  			}
  		}
  		if(null != parent){
  			parent.setEnd(currentChar);
  		}
  	}