Like I said in my comment, your question is confusing; if all you're trying to do is to notify the opponent when a player makes a move, the simplest implementation is to use a BlockingQueue. The Javadoc even has code examples, so it should be fairly easy to implement. In your case, whenever a player makes a move, you put an item in the queue, that the consumer picks up and notifies the opponent that is participating in the same game. You don't need to mess with low level thread constructs, and if you're even thinking of finding threads based on ids from a pool, you're doing it all wrong.
The BlockingQueue would work, but it involves busy wait, so I'm not a big fan of it. Instead, you can use the Observer design pattern; the JDK already has support for this. Following is an example that I made up:
public class Main extends Observable implements Observer {
private final int numCores = Runtime.getRuntime().availableProcessors();
private final ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(numCores);
public Main() {
addObserver(this);
}
public static void main(String[] args) throws InterruptedException {
new Main().execute();
}
private void execute() {
for (int i = 0; i < 5; ++i) {
this.setChanged();
this.notifyObservers(i);
try {
Thread.sleep(1000l);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
executor.shutdown();
}
@Override
public void update(Observable o, Object arg) {
System.out.printf("Received notification on thread: %s.\n", Thread.currentThread().getName());
executor.submit(() -> System.out.printf("Running in thread: %s, result: %s.\n",
Thread.currentThread().getName(), arg));
}
}
Received notification on thread: main.
Running in thread: pool-1-thread-1, result: 0.
Received notification on thread: main.
Running in thread: pool-1-thread-2, result: 1.
Received notification on thread: main.
Running in thread: pool-1-thread-3, result: 2.
Received notification on thread: main.
Running in thread: pool-1-thread-4, result: 3.
Received notification on thread: main.
Running in thread: pool-1-thread-5, result: 4.
Last but not the least, if you really want to take it up a notch, use messaging. You didn't mention if you're using a framework (again, lack of information on your part), but Spring supports messaging, so does Akka, Play and Camel.
