game loop that can bepaused / stopped, now using a Lock.

SomeClass.java

package com.example.foo;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class SomeClass {
  public static void main(final String[] args) {

    final Thread thread = new Thread(SomeClass::gameLoop);

    thread.start();

    new Thread(() -> {
      try {
        Thread.sleep(2000);
      } catch (final Exception e) {
        e.printStackTrace();
      }
      lock.lock();
      try {
        SomeClass.running = false;
        SomeClass.isGameRunning.signalAll();
      } finally {
        lock.unlock();
      }

      try {
        Thread.sleep(2000);
      } catch (final Exception e) {
        e.printStackTrace();
      }
      lock.lock();
      try {
        SomeClass.running = true;
        SomeClass.isGameRunning.signalAll();
      } finally {
        lock.unlock();
      }

    }).start();
  }

  static Lock lock = new ReentrantLock();
  static Condition isGameRunning = lock.newCondition();
  static volatile boolean running = true;

  private static void gameLoop() {
    try {
      if (!running) {
        System.out.println("paused!");
        lock.lock();
        try {
          SomeClass.isGameRunning.await();
        } finally {
          lock.unlock();
        }
      }
      Thread.sleep(500);
    } catch (final InterruptedException e) {
      return;
    }
    Thread.yield();
    System.out.println("pong");
    gameLoop();
  }

}