class Program12
    {
        static object obj = new object();
        static int lastNum = 4;
        static void WriteNum(object i)
        {
            //lock (obj)
            //{
            //Console.Write(i);  //輸出：1234 不加lock是無序的輸出 2134  1324 等
            //}
            //循環寫入10次 1234
            for
 
 (int k = 0; k < 10; k++)
            {
                lock (obj)
                {
                    if ((int)i == lastNum + 1|| (int)i == lastNum - 3)
                    {
                        if ((int)i==4)
                        {
                            Console.WriteLine(i);
                        }
                       
 
else
                        {
                            Console.Write(i);
                        }
                        lastNum = (int)i;
                        Monitor.PulseAll(obj);
                    }
                    else
                    {
                        k--;
                        Monitor.Wait(obj);
                    }
                }

            }
           

        }

        
 
static void Main(string[] args)
        {
            Thread t1 = new Thread(WriteNum);
            Thread t2 = new Thread(WriteNum);
            Thread t3 = new Thread(WriteNum);
            Thread t4 = new Thread(WriteNum);
            t1.Start(1);
            t2.Start(2);
            t3.Start(3);
            t4.Start(4);
            Console.ReadLine();
        }
    }

多線程（五）、同步訪問對象，循環打印1234