code: public String toStringWithoutLabels()
      {
          StringBuilder sb = new StringBuilder(size() * 4);
          int i = 1;
          for (IWord word : wordList)
          {
              if (word instanceof CompoundWord)
              {
                  int j = 0;
                  for (Word w : ((CompoundWord) word).innerList)
                  {
                      sb.append(w.getValue());
                      if (++j != ((CompoundWord) word).innerList.size())
                          sb.append(' ');
                  }
              }
              else
                  sb.append(word.getValue());
              if (i != wordList.size()) sb.append(' ');
              ++i;
          }
          return sb.toString();
      }
docs: 转换为空格分割无标签的String
  
  @return