問題描述

我使用java的延遲隊列來取數據，但是發現根本無法取出數據。

package com.test;import java.util.concurrent.Delayed;import java.util.concurrent.TimeUnit;public class SmsEntity implements Delayed { private final long WAIT_TIME = 10; private long startTime = System.currentTimeMillis(); private String phone; public SmsEntity(String phone) {this.phone = phone; } public String getPhone() {return phone; } public void setPhone(String phone) {this.phone = phone; } public long getStartTime() {return startTime; } public void setStartTime(long startTime) {this.startTime = startTime; } @Override public int compareTo(Delayed o) {SmsEntity entity = (SmsEntity) o;if (this.getStartTime() - entity.getStartTime() > 0) { return 1;}return -1; } @Override public long getDelay(TimeUnit unit) {//long waitTimeForGiveTimeUnit = unit.convert(WAIT_TIME, TimeUnit.MILLISECONDS);//long areadyLeftTime = unit.convert(System.currentTimeMillis(), TimeUnit.MILLISECONDS)//- unit.convert(startTime, TimeUnit.MILLISECONDS);//if (areadyLeftTime > waitTimeForGiveTimeUnit) {// return 0;//}//return unit.convert(waitTimeForGiveTimeUnit - areadyLeftTime, TimeUnit.MILLISECONDS);return 1; }}package com.test;import java.util.concurrent.DelayQueue;public class DelayQueueDemo { public static void main(String[] args) {DelayQueue<SmsEntity> queue=new DelayQueue<>();queue.put(new SmsEntity('1'));try {// Thread.sleep(3000); queue.put(new SmsEntity('2')); System.out.println(queue.take().getPhone()); System.out.println(queue.take().getPhone());} catch (InterruptedException e) { e.printStackTrace();} }}

結果是一直在阻塞。我想請教這是為什么，感覺自己調用的沒有錯啊

問題解答

getDelay()始終返回1，所以永遠不會expire。

可以仔細研究一下DelayQueue的文檔： https://docs.oracle.com/javas...

Expiration occurs when an element’s getDelay(TimeUnit.NANOSECONDS)method returns a value less than or equal to zero