java.util.LinkedList swQueue [] = new java.util.LinkedList [1];  //buffer for switches
        swQueue[0] = new java.util.LinkedList();
        swQueue[0].add(new packetX(1,2,"asdf"));
        packetX kk = new packetX();
        kk = swQueue[0].getFirst();   <<<< 這裡會編譯錯誤。
                System.out.println(kk.to);
class packetX extends java.lang.Object                 //Packet format
{
        //header
        public int to;
        public int from;
        //data
        public String data;
        public packetX()
        {}
        public packetX(int toX, int fromX, String dataX)
        {
            to = toX;
            from = fromX;
            data = dataX;
        }    }