Java DelayQueue实现任务延时示例讲解

import org.jetbrains.annotations.NotNull;
import java.util.Date;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
public class DelayEntity implements Delayed {
    private static final Long currentTime = System.currentTimeMillis();
    private String str;
    private Long scheduleTime;
    public DelayEntity(String str, Long delayed) {
        this.str = str;
        scheduleTime = System.currentTimeMillis() + (1000) * delayed;
    }
    @Override
    public long getDelay(@NotNull TimeUnit unit) {
        return unit.convert(scheduleTime - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
    }
    @Override
    public int compareTo(@NotNull Delayed o) {
        return (int) (this.scheduleTime - ((DelayEntity) o).scheduleTime);
    }
    public String getStr() {
        return str;
    }
    public Long getScheduleTime() {
        return scheduleTime;
    }
    public String showScheduleTime() {
        return "计划执行时间:" + new Date(this.scheduleTime).toString();
    }
}

@Test
    public void test() throws InterruptedException {
        DelayQueue<DelayEntity> delayQueue = new DelayQueue<>();
        delayQueue.put(new DelayEntity("1", 1l));
        delayQueue.put(new DelayEntity("2", 2l));
        delayQueue.put(new DelayEntity("4", 3l));
        while (true) {
            DelayEntity take = delayQueue.take();
            System.out.println("参数:" + take.getStr() + ";计划执行时间:" + take.showScheduleTime() + ";实际执行时间:" + new Date().toString());
        }
    }

public E take() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                E first = q.peek();
                if (first == null)
                    available.await();
                else {
                    long delay = first.getDelay(NANOSECONDS);
                    if (delay <= 0)
                        return q.poll();
                    first = null; // don't retain ref while waiting
                    if (leader != null)
                        available.await();
                    else {
                        Thread thisThread = Thread.currentThread();
                        leader = thisThread;
                        try {
                            available.awaitNanos(delay);
                        } finally {
                            if (leader == thisThread)
                                leader = null;
                        }
                    }
                }
            }
        } finally {
            if (leader == null && q.peek() != null)
                available.signal();
            lock.unlock();
        }
    }