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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();

        }

    }

}