Java ReentrantLock class

import java.util.concurrent.locks.ReentrantLock;

public class Main {

  public static void main(String args[]) {
    ReentrantLock lock = new ReentrantLock();

    new LockThread(lock, "A");
    new LockThread(lock, "B");

  }//ww  w . ja v  a 2s . com
}

// A shared resource.
class MyValue {
  static int count = 0;
}

// A thread of execution that increments count.
class LockThread implements Runnable {
  private String name;
  private ReentrantLock lock;

  public LockThread(ReentrantLock lk, String n) {
    lock = lk;
    name = n;
    new Thread(this).start();
  }

  public void run() {

    System.out.println("Starting " + name);

    try {
      // First, lock count.
      System.out.println(name + " is waiting to lock count.");
      lock.lock();
      System.out.println(name + " is locking count.");

      MyValue.count++;
      System.out.println(name + ": " + MyValue.count);

      // Now, allow a context switch -- if possible.
      System.out.println(name + " is sleeping.");
      Thread.sleep(1000);
    } catch (InterruptedException exc) {
      System.out.println(exc);
    } finally {
      // Unlock
      System.out.println(name + " is unlocking count.");
      lock.unlock();
    }
  }
}