多线程-同步模式 保护性暂停

public class test02 {
    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < 3; i++) {
            new People().start();
        }
        Thread.sleep(1000);
        for (Integer id : Mailboxes.getIds()) {
            new Postman(id, "内容" + id).start();
        }
    }
}

@Slf4j
class People extends Thread {
    @Override
    public void run() {
        // 收信
        GuardedObject guardedObject = Mailboxes.createGuardedObject();
        log.debug("开始收信 id:{}", guardedObject.getId());
        Object mail = guardedObject.get(5000);
        log.debug("收到信 id:{}, 内容:{}", guardedObject.getId(), mail);
    }
}

@Slf4j
class Postman extends Thread {
    private int id;
    private String mail;

    public Postman(int id, String mail) {
        this.id = id;
        this.mail = mail;
    }

    @Override
    public void run() {
        GuardedObject guardedObject = Mailboxes.getGuardedObject(id);
        log.debug("送信 id:{}, 内容:{}", id, mail);
        guardedObject.set(mail);
    }
}

class Mailboxes {
    private static Map<Integer, GuardedObject> boxes = new Hashtable<>();
    private static int id = 1;

    // 产生唯一 id
    private static synchronized int generateId() {
        return id++;
    }

    public static GuardedObject getGuardedObject(int id) {
        return boxes.remove(id);
    }

    public static GuardedObject createGuardedObject() {
        GuardedObject go = new GuardedObject(generateId());
        boxes.put(go.getId(), go);
        return go;
    }

    public static Set<Integer> getIds() {
        return boxes.keySet();
    }
}

class GuardedObject {
    private int id;
    private Object response;

    public int getId() {
        return id;
    }

    public GuardedObject(int id) {
        this.id = id;
    }


    @SneakyThrows
    public Object get(long timeout) {
        synchronized (this) {
            long begin = System.currentTimeMillis();
            long passedTime = 0;
            while (Objects.isNull(response)) {
                long wait = timeout - passedTime;
                if (wait <= 0) {
                    break;
                }
                this.wait(wait);
                passedTime = System.currentTimeMillis() - begin;
            }
            return response;
        }
    }

    @SneakyThrows
    public void set(Object response) {
        synchronized (this) {
            this.response = response;
            this.notifyAll();
        }
    }
}