Java Collections - DelayQueue.poll() Examples

package com.logicbig.example.delayqueue;

import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;

public class PollExample {

    public static void main(String... args) throws InterruptedException {
        DelayQueue<Task> dq = new DelayQueue<>();
        dq.offer(new Task(1));
        dq.offer(new Task(2));
        dq.offer(new Task(3));

        int c = 0;
        while (true) {
            Task task = dq.poll();
            if (task == null) {
                continue;
            }
            c++;
            System.out.println(task);
            System.out.println("----");
            if (c == 3) {
                break;
            }
        }
    }

    private static class Task implements Delayed {
        private final long end;
        private final int expectedDelay;
        private int id;

        Task(int id) {
            this.id = id;
            expectedDelay = ThreadLocalRandom.current().nextInt(100, 1000);
            end = System.currentTimeMillis() + expectedDelay;
        }

        @Override
        public long getDelay(TimeUnit unit) {
            return unit.convert(end - System.currentTimeMillis(),
                    TimeUnit.MILLISECONDS);
        }

        @Override
        public int compareTo(Delayed o) {
            return Long.compare(this.getDelay(TimeUnit.MILLISECONDS),
                    o.getDelay(TimeUnit.MILLISECONDS));
        }

        @Override
        public String toString() {
            return "Task{" +
                    "expectedDelay=" + expectedDelay +
                    ", id=" + id +
                    '}';
        }
    }
}