/*

  * To change this template, choose Tools | Templates

  * and open the template in the editor.

  */

 package api;

 import java.util.concurrent.locks.Lock;

 import java.util.concurrent.locks.ReentrantLock;

 /**

  *

  * @author Jaroslav Tulach <jaroslav.tulach@netbeans.org>

  */

 public class Mutex {

     Lock lock = new ReentrantLock();

     public Mutex() {

     }

     public void readAccess(Runnable r) {

         try {

             lock.lock();

             r.run();

         } finally {

             lock.unlock();

         }

     }

     public Mutex(Privileged privileged) {

         if (privileged.mutex != null) {

             throw new IllegalStateException();

         }

         privileged.mutex = this;

     }

     public static final class Privileged {

         private Mutex mutex;

         public void enterReadAccess() {

             mutex.lock.lock();

         }

         public void exitReadAccess() {

             mutex.lock.unlock();

         }

     }

 }