code: public void reassignOutgoingTransition(char letter, MDAGNode oldTargetNode, MDAGNode newTargetNode)
      {
          oldTargetNode.incomingTransitionCount--;
          newTargetNode.incomingTransitionCount++;
          
          outgoingTransitionTreeMap.put(letter, newTargetNode);
      }
docs: 重新设置转移状态函数的目标
  Reassigns the target node of one of this node's outgoing transitions.
  
  @param letter            the char which labels the outgoing _transition of interest
  @param oldTargetNode     the MDAGNode that is currently the target of the _transition of interest
  @param newTargetNode     the MDAGNode that is to be the target of the _transition of interest