OnJava8-Examples/concurrency/NotifyVsNotifyAll.java

// concurrency/NotifyVsNotifyAll.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.
import java.util.concurrent.*;
import java.util.*;

class Blocker {
  synchronized void waitingCall() {
    try {
      while(!Thread.interrupted()) {
        wait();
        System.out.print(Thread.currentThread() + " ");
      }
    } catch(InterruptedException e) {
      // OK to exit this way
    }
  }
  synchronized void prod() { notify(); }
  synchronized void prodAll() { notifyAll(); }
}

class Task implements Runnable {
  static Blocker blocker = new Blocker();
  @Override
  public void run() { blocker.waitingCall(); }
}

class Task2 implements Runnable {
  // A separate Blocker object:
  static Blocker blocker = new Blocker();
  @Override
  public void run() { blocker.waitingCall(); }
}

public class NotifyVsNotifyAll {
  public static void main(String[] args) throws Exception {
    ExecutorService exec = Executors.newCachedThreadPool();
    for(int i = 0; i < 5; i++)
      exec.execute(new Task());
    exec.execute(new Task2());
    Timer timer = new Timer();
    timer.scheduleAtFixedRate(new TimerTask() {
      boolean prod = true;
      @Override
      public void run() {
        if(prod) {
          System.out.print("\nnotify() ");
          Task.blocker.prod();
          prod = false;
        } else {
          System.out.print("\nnotifyAll() ");
          Task.blocker.prodAll();
          prod = true;
        }
      }
    }, 400, 400); // Run every .4 second
    TimeUnit.SECONDS.sleep(5); // Run for a while...
    timer.cancel();
    System.out.println("\nTimer canceled");
    TimeUnit.MILLISECONDS.sleep(500);
    System.out.print("Task2.blocker.prodAll() ");
    Task2.blocker.prodAll();
    TimeUnit.MILLISECONDS.sleep(500);
    System.out.println("\nShutting down");
    exec.shutdownNow(); // Interrupt all tasks
  }
}
/* Output:
notify() Thread[pool-1-thread-1,5,main]
notifyAll() Thread[pool-1-thread-1,5,main]
Thread[pool-1-thread-5,5,main]
Thread[pool-1-thread-4,5,main]
Thread[pool-1-thread-3,5,main]
Thread[pool-1-thread-2,5,main]
notify() Thread[pool-1-thread-1,5,main]
notifyAll() Thread[pool-1-thread-1,5,main]
Thread[pool-1-thread-2,5,main]
Thread[pool-1-thread-3,5,main]
Thread[pool-1-thread-4,5,main]
Thread[pool-1-thread-5,5,main]
notify() Thread[pool-1-thread-1,5,main]
notifyAll() Thread[pool-1-thread-1,5,main]
Thread[pool-1-thread-5,5,main]
Thread[pool-1-thread-4,5,main]
Thread[pool-1-thread-3,5,main]
Thread[pool-1-thread-2,5,main]
notify() Thread[pool-1-thread-1,5,main]
notifyAll() Thread[pool-1-thread-1,5,main]
Thread[pool-1-thread-2,5,main]
Thread[pool-1-thread-3,5,main]
Thread[pool-1-thread-4,5,main]
Thread[pool-1-thread-5,5,main]
notify() Thread[pool-1-thread-1,5,main]
notifyAll() Thread[pool-1-thread-1,5,main]
Thread[pool-1-thread-5,5,main]
Thread[pool-1-thread-4,5,main]
Thread[pool-1-thread-3,5,main]
Thread[pool-1-thread-2,5,main]
notify() Thread[pool-1-thread-1,5,main]
notifyAll() Thread[pool-1-thread-1,5,main]
Thread[pool-1-thread-2,5,main]
Thread[pool-1-thread-3,5,main]
Thread[pool-1-thread-4,5,main]
Thread[pool-1-thread-5,5,main]
Timer canceled
Task2.blocker.prodAll() Thread[pool-1-thread-6,5,main]
Shutting down
*/