ex-20-04

Programming Csharp Source Code(代码) Programming Csharp Source Code

// Example 20-04: Using a Monitor object

namespace Programming_CSharp
{
   using System;
   using System.Threading;

   class Tester
   {
      static void Main()
      {
         // make an instance of this class
         Tester t = new Tester();

         // run outside static Main
         t.DoTest();                 
      }

      public void DoTest()
      {
         // create an array of unnamed threads
         Thread[] myThreads = 
            {
               new Thread( new ThreadStart(Decrementer) ),
               new Thread( new ThreadStart(Incrementer) )              
            };

         // start each thread
         int ctr = 1;
         foreach (Thread myThread in myThreads)
         {
            myThread.IsBackground=true;
            myThread.Start();
            myThread.Name = "Thread" + ctr.ToString();
            ctr++;
            Console.WriteLine("Started thread {0}", myThread.Name);
            Thread.Sleep(50);
         }

         // wait for all threads to end before continuing
         foreach (Thread myThread in myThreads)
         {
            myThread.Join();
         }

         // after all threads end, print a message
         Console.WriteLine("All my threads are done.");
      }

      void Decrementer()
      {
         try 
         {
            // synchronize this area of code
            Monitor.Enter(this);

            // if counter is not yet 10
            // then free the monitor to other waiting
            // threads, but wait in line for your turn
            if (counter < 10)
            {
               Console.WriteLine(
                  "[{0}] In Decrementer. Counter: {1}. Gotta Wait!",
                  Thread.CurrentThread.Name, counter);
               Monitor.Wait(this);
            }

            while (counter >0)
            {
               long temp = counter;
               temp--;
               Thread.Sleep(1);
               counter = temp;
               Console.WriteLine(
                  "[{0}] In Decrementer. Counter: {1}. ",
                  Thread.CurrentThread.Name, counter);

            }
         }
         finally
         {
            Monitor.Exit(this);
         }
      }

      void Incrementer()
      {
         try
         {
            Monitor.Enter(this);
            while (counter < 10)
            {
               long temp = counter;
               temp++;
               Thread.Sleep(1);
               counter = temp;
               Console.WriteLine(
                  "[{0}] In Incrementer. Counter: {1}",
                  Thread.CurrentThread.Name, counter);
            }

            // I'm done incrementing for now, let another
            // thread have the Monitor
            Monitor.Pulse(this);
         }
         finally
         {
            Console.WriteLine("[{0}] Exiting...",
               Thread.CurrentThread.Name);
            Monitor.Exit(this);
         }
      }
      private long counter = 0;
   }
}