code: public void printGraph() {
          for (Term term : terms) {
              if (term == null) {
                  continue;
              }
              System.out.print(term.getName() + "\t" + term.score() + " ,");
              while ((term = term.next()) != null) {
                  System.out.print(term + "\t" + term.score() + " ,");
              }
              System.out.println();
          }
      }
docs: 对graph进行调试用的