// concurrency/waxomatic2/WaxOMatic2.java
// ©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.
// Using Lock and Condition objects.
package concurrency.waxomatic2;
import java.util.concurrent.*;
import java.util.concurrent.locks.*;

class Car {
  private Lock lock = new ReentrantLock();
  private Condition condition = lock.newCondition();
  private boolean waxOn = false;
  public void waxed() {
    lock.lock();
    try {
      waxOn = true; // Ready to buff
      condition.signalAll();
    } finally {
      lock.unlock();
    }
  }
  public void buffed() {
    lock.lock();
    try {
      waxOn = false; // Ready for another coat of wax
      condition.signalAll();
    } finally {
      lock.unlock();
    }
  }
  public void waitForWaxing() throws InterruptedException {
    lock.lock();
    try {
      while(waxOn == false)
        condition.await();
    } finally {
      lock.unlock();
    }
  }
  public void waitForBuffing() throws InterruptedException{
    lock.lock();
    try {
      while(waxOn == true)
        condition.await();
    } finally {
      lock.unlock();
    }
  }
}

class WaxOn implements Runnable {
  private Car car;
  public WaxOn(Car c) { car = c; }
  @Override
  public void run() {
    try {
      while(!Thread.interrupted()) {
        System.out.print("Wax On! ");
        TimeUnit.MILLISECONDS.sleep(200);
        car.waxed();
        car.waitForBuffing();
      }
    } catch(InterruptedException e) {
      System.out.println("Exiting via interrupt");
    }
    System.out.println("Ending Wax On task");
  }
}

class WaxOff implements Runnable {
  private Car car;
  public WaxOff(Car c) { car = c; }
  @Override
  public void run() {
    try {
      while(!Thread.interrupted()) {
        car.waitForWaxing();
        System.out.print("Wax Off! ");
        TimeUnit.MILLISECONDS.sleep(200);
        car.buffed();
      }
    } catch(InterruptedException e) {
      System.out.println("Exiting via interrupt");
    }
    System.out.println("Ending Wax Off task");
  }
}

public class WaxOMatic2 {
  public static void main(String[] args) throws Exception {
    Car car = new Car();
    ExecutorService exec = Executors.newCachedThreadPool();
    exec.execute(new WaxOff(car));
    exec.execute(new WaxOn(car));
    TimeUnit.SECONDS.sleep(5);
    exec.shutdownNow();
  }
}
/* Output:
Wax On! Wax Off! Wax On! Wax Off! Wax On! Wax Off! Wax On!
Wax Off! Wax On! Wax Off! Wax On! Wax Off! Wax On! Wax Off!
Wax On! Wax Off! Wax On! Wax Off! Wax On! Wax Off! Wax On!
Wax Off! Wax On! Wax Off! Wax On! Exiting via interrupt
Exiting via interrupt
Ending Wax On task
Ending Wax Off task
*/