using System;
using System.Threading;

namespace ClassExamples {
   class Tester {
      int x;

      public void Inc() {
         for (int i=0; i<10; i++) {
            lock(this) {
               x++;
               Console.WriteLine(x);
            }
         }
      }
      public void Dec() {
         for (int i=0; i<10; i++) {
            lock(this) {
               x--;
               Console.WriteLine(x);
            }
         }
      }

      public static void Main() {
         Tester tester = new Tester();

         Thread tInc = new Thread(new ThreadStart(tester.Inc));
         Thread tDec = new Thread(new ThreadStart(tester.Dec));

         tInc.Start();
         tDec.Start();

         Thread.Sleep(500);

         tInc.Abort();
         tDec.Abort();

         tInc.Join();
         tDec.Join();
      }
   }
}