package dk.itu.voop.thread;

public class WaitNotifyTest {

   static class SharedState {
      public void letsWait() throws InterruptedException {
         trace("waiting for lock");
         synchronized(this) {
            trace("holding lock");
            trace("spending some time");
            Thread.sleep(100);
            trace("calling wait()");
            trace("giving up lock");
            trace("blocks...");
            wait();
            trace("woke up");
            trace("holding lock again");
            trace("returned from wait");
         }
         trace("no longer holding lock");
      }
      public void notifyWaiter() throws InterruptedException {
         trace("waiting for lock");
         synchronized(this) {
            trace("holding lock");
            trace("calling notify()");
            notify();
            trace("returned from notify");
            trace("spending some time");
            Thread.sleep(100);
            trace("giving up lock");
            trace("waking up other thread");
         }
         trace("no longer holding lock");
      }
   }

   static class Waiter implements Runnable {
      SharedState _sharedState;
      Waiter(SharedState sharedState) { _sharedState = sharedState; }
      public void run() {
         try {
            _sharedState.letsWait();
         }
         catch(InterruptedException e) {
            trace("was interrupted");
         }
      }
   }

   static class Notifier implements Runnable {
      SharedState _sharedState;
      Notifier(SharedState sharedState) { _sharedState = sharedState; }
      public void run() {
         try {
            _sharedState.notifyWaiter();
         }
         catch(InterruptedException e) {
            trace("was interrupted");
         }
      }
   }

   public static void main(String[] args) throws InterruptedException {
      SharedState sharedState = new SharedState();
      Thread waiterThread = new Thread(new Waiter(sharedState), "waiter");
      Thread notifierThread = new Thread(new Notifier(sharedState), "notifier");
      waiterThread.start();
      Thread.sleep(50);
      notifierThread.start();
   }

   static void trace(String msg) {
      System.out.println(Thread.currentThread().getName() + ": " + msg);
   }

}

/*
$ ./runwaitnotify.sh
waiter: waiting for lock
waiter: holding lock
waiter: spending some time
notifier: waiting for lock
waiter: calling wait()
waiter: giving up lock
waiter: blocks...
notifier: holding lock
notifier: calling notify()
notifier: returned from notify
notifier: spending some time
notifier: giving up lock
notifier: waking up other thread
waiter: woke up
waiter: holding lock again
waiter: returned from wait
waiter: no longer holding lock
notifier: no longer holding lock
*/