public class Main {
  public static void main(String[] args) {
    Clerk clerk = new Clerk();
    new Thread(new Producer(clerk)).start();
    new Thread(new Consumer(clerk)).start();
  }
}

class Clerk {
  private int product = 0;

  public synchronized int getProduct() {
    if (this.product > 1) {
      System.err.println("產品超過1個, " + product);
      System.exit(0);
    }
    if (this.product < 1) {
      try {
        this.wait();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
    this.product = this.product - 1;
    int product2 = this.product;
    this.notify();
    return product2;
  }

  public synchronized int addProduct() {
    if (this.product > 1) {
      System.err.println("產品超過1個, " + product);
      System.exit(0);
    }
    if (this.product > 0) {
      try {
        this.wait();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
    this.product = this.product + 1;
    int product2 = this.product;
    this.notify();
    return product2;
  }
}

class Producer implements Runnable {
  private Clerk clerk;

  public Producer(Clerk clerk) {
    this.clerk = clerk;
  }

  @Override
  public void run() {
    while (true) {
      int product = clerk.addProduct();
      System.out.println("生產者生產 1 個商品, 目前剩下的商品數量 " + product);
    }
  }
}

class Consumer implements Runnable {
  private Clerk clerk;

  public Consumer(Clerk clerk) {
    this.clerk = clerk;
  }

  @Override
  public void run() {
    while (true) {
      int product = clerk.getProduct();
      System.out.println("消費者拿到 1 個商品, 目前剩下的商品數量 " + product);
    }
  }
}