生产者/消费者 - synchronized

public class SynchronizedDemo {

    //类似包子铺场景：包子最多提前做好50个，卖出去5个就再做；卖完了，买包子的就得等着
    //Synchronized版本

    private static int MAX = 50;
    private int number = 0;

    public void produce() throws InterruptedException {
        while (true) {
            synchronized (this) {
                if (number == MAX) {
                    //释放锁，出让cpu时间片，线程状态 - WAITING，等待唤醒
                    this.wait();
                    continue;
                }
                number++;
                System.out.println("+++++第 " + number + " 个包子被做出来了！ - " + Thread.currentThread().getName());
                if (number > 20) {
                    //做出包子超过20个，买包子的赶紧买
                    this.notifyAll();
                }
            }
        }
    }

    public void consume() throws InterruptedException {
        while (true) {
            synchronized (this) {
                if (number == 0) {
                    //释放锁，出让cpu时间片，线程状态 - WAITING，等待唤醒
                    this.wait();
                    continue;
                }
                System.out.println("-----第 " + number + "个包子被买了！ - " + Thread.currentThread().getName());
                number--;
                if (number < MAX - 5) {
                    //包子空缺超过5个，通知做包子的赶紧做
                    this.notifyAll();
                }
            }
        }
    }

    public static void main(String[] args) {
        SynchronizedDemo synchronizedDemo = new SynchronizedDemo();
        //5个做包子的
        for (int i = 0; i < 5; i++) {
            new Thread(() -> {
                try {
                    synchronizedDemo.produce();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }
        //20个买包子的
        for (int i = 0; i < 20; i++) {
            new Thread(() -> {
                try {
                    synchronizedDemo.consume();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}