Program in JAVA to implement Mutual Exclusion.

public class Counter_locks implements Runnable {

      int count = 0;

     public Counter_locks() { 

     }

     public synchronized void run()  //synchronizes the run method

     {

         System.out.println(Thread.currentThread().getName() + ": " + "Current Value of count = " + count);

         System.out.println(Thread.currentThread().getName() + " increments count....");

         count ++;

        try {

                             Thread.currentThread().sleep(1000);

         } catch (InterruptedException e) {

             System.out.println("Thread " + Thread.currentThread().getName() + "interrupted.");

         }

         System.out.println("Value of count after incremented by thread "

         + Thread.currentThread().getName() + " = " + count);

     }

     public static void main(String args[]) {

         Counter_locks c = new Counter_locks();

  

         Thread t1 = new Thread(c);

         Thread t2 = new Thread(c);

         Thread t3 = new Thread(c);

         Thread t4 = new Thread(c);

  

         t1.setName("Thread 1");

         t2.setName("Thread 2");

         t3.setName("Thread 3");

         t4.setName("Thread 4");

  

         t1.start();

         t2.start();

         t3.start();

         t4.start();

  

         try {

             t1.join();

             t2.join();

             t3.join();

             t4.join();

         }

         catch (InterruptedException e) {

             System.out.println("Main thread Interrupted .....");

         }

  

         System.out.println("Main thread exits.....");

     }

 }

Output :

D:\>javac  Counter_locks.java

D:\>java Counter_locks

Thread 1: Current Value of count = 0

Thread 1 increments count....

Value of count after incremented by thread Thread 1 = 1

Thread 4: Current Value of count = 1

Thread 4 increments count....

Value of count after incremented by thread Thread 4 = 2

Thread 3: Current Value of count = 2

Thread 3 increments count....

Value of count after incremented by thread Thread 3 = 3

Thread 2: Current Value of count = 3

Thread 2 increments count....

Value of count after incremented by thread Thread 2 = 4

Main thread exits.....