code: public void remove(String key)
      {
          BaseNode branch = this;
          char[] chars = key.toCharArray();
          for (int i = 0; i < chars.length - 1; ++i)
          {
              if (branch == null) return;
              branch = branch.getChild(chars[i]);
          }
          if (branch == null) return;
          // 最后一个字设为undefined
          if (branch.addChild(new Node(chars[chars.length - 1], Status.UNDEFINED_0, value)))
          {
              --size;
          }
      }
docs: 删除一个词
  
  @param key