Guarded Suspension Pattern【其他模式】

Guarded Suspension Pattern

public class GuardedSuspension {
    /**
     * Guarded Suspension Pattern【保护悬挂模式】：如果目标对象不在指定的状态下，则执行警戒方法时，
     *  当前线程将阻塞等待，直到目标对象进入指定状态为止。
     */
    @Test
    public void all() throws InterruptedException {
        final Disk disk = new Disk();
        CompletableFuture.runAsync(() -> new Consumer(disk).consume());
        TimeUnit.SECONDS.sleep(2);
        new Produer(disk).produce();
        TimeUnit.SECONDS.sleep(2);
    }
}

@AllArgsConstructor
@Slf4j
class Consumer {
    private final Disk disk;

    public void consume() {
        synchronized (disk) {
            if (disk.empty()) {
                log.info("current thread is waiting now. {}", Thread.currentThread().getName());
                try {
                    disk.wait();
                    log.info("take item {}", disk.take());
                } catch (final InterruptedException e) {
                    log.error("Interrupted", e);
                }
            }
        }
    }
}

@AllArgsConstructor
class Produer {
    private final Disk disk;

    public void produce() {
        synchronized (disk) {
            if (disk.empty()) {
                disk.put(Thread.currentThread().getName());
                disk.notify();
            }
        }
    }
}

class Disk {
    private transient String item;

    public boolean empty() {
        return StringUtils.isBlank(item);
    }

    public String take() {
        final String take = item;
        item = null;
        return take;
    }

    public void put(String item) {
        if (StringUtils.isBlank(item)) {
            throw new IllegalStateException("invalid item ");
        }
        this.item = item;
    }
}