code: public boolean contains(String str)
      {
          if (sourceNode != null)      //if the MDAG hasn't been simplified
          {
              MDAGNode targetNode = sourceNode.transition(str.toCharArray());
              return (targetNode != null && targetNode.isAcceptNode());
          }
          else
          {
              SimpleMDAGNode targetNode = simplifiedSourceNode.transition(mdagDataArray, str.toCharArray());
              return (targetNode != null && targetNode.isAcceptNode());
          }
      }
docs: 是否包含<br>
  Determines whether a String is present in the MDAG.
  
  @param str the String to be searched for
  @return true if {@code str} is present in the MDAG, and false otherwise