面试题之多线程实现生产者消费者模式

notify方法何时执行？当前线程进入等待状态时notify方法才可以执行。

package ThreadTest;

import java.util.linkedList;

public class 生产者消费者 {
    static int carNumber = 1;
    public static void main(String[] args) {
        Car4s car4s = new Car4s();
        new Thread(new ProductTask(car4s),"汽车生产商1").start();
        new Thread(new ConsumerTask(car4s),"汽车销售店1").start();
        new Thread(new ProductTask(car4s),"汽车生产商2").start();
        new Thread(new ProductTask(car4s),"汽车生产商3").start();
    }
    static class Car{ //汽车
        int name;
        public int getName() {
            return name;
        }
        public void setName(int name) {
            this.name = name;
        }
    }
    static class Car4s{ //4s店
        linkedList CarList = new linkedList();
    }
    static class ProductTask implements Runnable{  //生产商
        Car4s car4s;
        public ProductTask(Car4s carList) {
            this.car4s = carList;
        }
        @Override
        public void run() {
                while(true){
                    synchronized (car4s) {
                        if (car4s.CarList.size() < 4) {
                            Car car = new Car();
                            car.setName(carNumber);
                            car4s.CarList.push(car);
//                          System.out.println(car4s);
                            System.out.println(Thread.currentThread().getName()+"生产了汽车" + car.getName());
                            carNumber++;
                            car4s.notifyAll();
                        } else {
                            try {
                                car4s.wait(); //先进入等待状态才可以唤醒其他线程
                            } catch (InterruptedException e) {
                                System.out.println("睡眠失败");
                            }
                        }
                    }
                }

        }
    }
    static class ConsumerTask implements Runnable{  //消费者
        Car4s car4s;
        public ConsumerTask(Car4s carList) {
            this.car4s = carList;
        }
        @Override
        public void run() {
                while(true){
                    synchronized (car4s) {
                        if (car4s.CarList.size() > 0) {
                            Car Buycar = (Car) car4s.CarList.poll();
//                            System.out.println(car4s);
                            System.out.println(Thread.currentThread().getName()+"出售了汽车" + Buycar.getName());
                            car4s.notifyAll();
                        } else {
                            try {
                                car4s.wait();
                            } catch (InterruptedException e) {
                                System.out.println("睡眠失败");
                            }
                        }
                    }
                }

        }
    }
}