Create a dead lock - Java Thread

Java examples for Thread:synchronized

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Description

Create a dead lock

Demo Code

class _01DeadLockTest {

  public static void main(String[] args) {
    Thread thread1 = new Thread(new A(), "Thread-1");
    Thread thread2 = new Thread(new B(), "Thread-2");
    thread1.start();//from w  w  w  . j  a  v a  2  s .  co m
    thread2.start();
  }

}

class A implements Runnable {
  public void run() {

    synchronized (String.class) {

      /*
       * Adding this optional delay so that Thread-2 could enough time to
       * lock Object class and form deadlock. If you remove this sleep,
       * because of threads unpredictable behavior it might that Thread-1
       * gets completed even before Thread-2 is started and we will never
       * form deadLock.
       */
      try {

        Thread.sleep(200);

//        new Scanner(System.in).next();
//        System.exit(0);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }

      System.out.println(Thread.currentThread().getName() + "has acquired lock "
          + "on String class and waiting to acquire lock on Object class...");
      synchronized (Object.class) {
        System.out.println(Thread.currentThread().getName() + " has acquired lock on Object class");
      }
    }

    System.out.println(Thread.currentThread().getName() + " has ENDED");
  }
}

class B extends Thread {
  public void run() {

    synchronized (Object.class) {
      System.out.println(Thread.currentThread().getName() + " has acquired "
          + "lock on Object class and waiting to acquire lock on String class...");

      /*
       * Adding this optional delay so that Thread-1 could enough time to
       * lock String class and form deadlock. If you remove this sleep,
       * because of threads unpredictable behavior it might that Thread-2
       * gets completed even before Thread-1 is started and we will never
       * form deadLock.
       */
      try {
        Thread.sleep(100);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }

      synchronized (String.class) {
        System.out.println(Thread.currentThread().getName() + " has acquired lock on String class");
      }
    }

    System.out.println(Thread.currentThread().getName() + " has ENDED");
  }
}

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