// threads/ExplicitCriticalSection.java

// (c)2016 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://mindviewinc.com/Books/OnJava/ for more book information.

// {ThrowsException} on a multiprocessor machine

// Using explicit Lock objects to create critical sections

// {java threads.ExplicitCriticalSection}

package threads;

import java.util.concurrent.locks.*;

// Synchronize the entire method:

class ExplicitPairManager1 extends PairManager {

private Lock lock = new ReentrantLock();

@Override

public void increment() {

lock.lock();

try {

p.incrementX();

p.incrementY();

store(getPair());

} finally {

lock.unlock();

}

}

}

// Use a critical section:

class ExplicitPairManager2 extends PairManager {

private Lock lock = new ReentrantLock();

@Override

public void increment() {

Pair temp;

lock.lock();

try {

p.incrementX();

p.incrementY();

temp = getPair();

} finally {

lock.unlock();

}

store(temp);

}

}

public class ExplicitCriticalSection {

public static void

main(String[] args) throws Exception {

PairManager

pman1 = new ExplicitPairManager1(),

pman2 = new ExplicitPairManager2();

CriticalSection.testApproaches(pman1, pman2);

}

}

/* Output:

pm1: Pair: x: 10, y: 10 checkCounter = 1713716

pm2: Pair: x: 10, y: 10 checkCounter = 1717747

___[ Error Output ]___

Exception in thread "pool-1-thread-4" Exception in thread

"pool-1-thread-3" threads.Pair$PairValuesNotEqualException:

Pair values not equal: x: 2, y: 1

at threads.Pair.checkState(CriticalSection.java:37)

at

threads.PairChecker.run(CriticalSection.java:111)

at java.util.concurrent.ThreadPoolExecutor.runWorke

r(ThreadPoolExecutor.java:1142)

at java.util.concurrent.ThreadPoolExecutor$Worker.r

un(ThreadPoolExecutor.java:617)

at java.lang.Thread.run(Thread.java:745)

threads.Pair$PairValuesNotEqualException: Pair values not

equal: x: 2, y: 1

at threads.Pair.checkState(CriticalSection.java:37)

at

threads.PairChecker.run(CriticalSection.java:111)

at java.util.concurrent.ThreadPoolExecutor.runWorke

r(ThreadPoolExecutor.java:1142)

at java.util.concurrent.ThreadPoolExecutor$Worker.r

un(ThreadPoolExecutor.java:617)

at java.lang.Thread.run(Thread.java:745)

*/