ReentrantLockFairnessDemo.java

import java.util.concurrent.locks.ReentrantLock;

public class ReentrantLockFairnessDemo {

    private static ReentrantLock reentrantLock = new ReentrantLock(true);

    public static void main(String[] args) throws InterruptedException {

        ReentrantLockFairnessDemo reentrantLockDemo = new ReentrantLockFairnessDemo();

        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                reentrantLockDemo.checkSync();
            }
        });

        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                reentrantLockDemo.checkSync();
            }
        });

        Thread t3 = new Thread(new Runnable() {
            @Override
            public void run() {
                reentrantLockDemo.checkSync();
            }
        });

        t1.start();
        Thread.sleep(1000);
        t2.start();
        Thread.sleep(1000);
        t3.start();

        t1.join();
        t2.join();
        t3.join();

        System.out.println("Finished..");
    }

    private void checkSync() {

        reentrantLock.lock();

        System.out.println("Acquired.." + reentrantLock.toString());
        try {
            Thread.sleep(5000);
            System.out.println("Done..");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        reentrantLock.unlock();
    }
}