SimpleLockTest.java

import java.util.concurrent.locks.ReentrantLock;

public class SimpleLockTest
{
 public static void main(String[] args) throws InterruptedException
 {
 final Object lock1 = new Object();
 new SynchronizedBlockLockUser(lock1, "Sfirst").start();
 Thread.sleep(100);
 new SynchronizedBlockLockUser(lock1, "Ssecond").start();

 ReentrantLock lock2 = new ReentrantLock();
 new ReentrantLockUser(lock2, "Rfirst").start();
 Thread.sleep(100);
 new ReentrantLockUser(lock2, "Rsecond").start();
 }
}

class SynchronizedBlockLockUser extends Thread
{
 private final Object lock;

 public SynchronizedBlockLockUser(Object lock, String name)
 {
 super(name);
 this.lock = lock;
 }

 @Override
 public void run()
 {
 try
 {
 while (true)
 {
 Thread.sleep(100);
 synchronized (lock)
 {
 System.out.println("Lock acquired by thread: " + getName());
 System.out.println("Holding lock for 3 sec");
 Thread.sleep(3000);
 }
 }
 }
 catch (Exception ignored) { }
 }
}

class ReentrantLockUser extends Thread
{
 private final ReentrantLock lock;

 public ReentrantLockUser(ReentrantLock lock, String name)
 {
 super(name);
 this.lock = lock;
 }

 @Override
 public void run()
 {
 try
 {
 while (true)
 {
 Thread.sleep(100);
 lock.lock();
 System.out.println("Lock acquired by thread: " + getName());
 System.out.println("Holding lock for 3 sec");
 Thread.sleep(3000);
 lock.unlock();
 }
 }
 catch (Exception ignored) { }
 finally
 {
 if(lock.isHeldByCurrentThread())
 lock.unlock();
 }
 }
}