Java如何使用DelayQueue实现队列？
BlockingQueue接口的实现中的java.util.concurrent.DelayQueue类。添加到队列中的元素必须实现java.util.concurrent.Delayed接口。
队列的大小不受限制，可以使添加立即返回，只有在延迟时间到期后才能从队列中获取元素。如果多个元素的延迟过期，则将首先使用延迟过期时间最长的元素。
package org.nhooo.example.util.concurrent;
import java.util.Random;
import java.util.UUID;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.DelayQueue;
public class DelayQueueExample {
public static void main(String[] args) {
// 使用DelayQueue创建阻塞队列的实例。
final BlockingQueue<DelayObject> queue = new DelayQueue<>();
final Random random = new Random();
new Thread(new Runnable() {
@Override
public void run() {
while (true) {
try {
// 将一些延迟的对象放入队列。
int delay = random.nextInt(10000);
DelayObject object = new DelayObject(UUID.randomUUID().toString(), delay);
System.out.printf("Put object = %s%n", object);
queue.put(object);
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}, "Producer Thread").start();
new Thread(new Runnable() {
@Override
public void run() {
while (true) {
try {
// 从DelayQueue对象中取出元素。
DelayObject object = queue.take();
System.out.printf("[%s] - Take object = %s%n",
Thread.currentThread().getName(), object);
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}, "Consumer Thread-1").start();
new Thread(new Runnable() {
@Override
public void run() {
while (true) {
try {
// 从DelayQueue对象中取出元素。
DelayObject object = queue.take();
System.out.printf("[%s] - Take object = %s%n",Thread.currentThread().getName(), object);
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}, "Consumer Thread-2").start();
}
}下面是该Delayed接口的实现。在实现类中，我们必须实现getDelay(TimeUnit)和compareTo(Object)方法。
package org.nhooo.example.util.concurrent;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
public class DelayObject implements Delayed {
private String data;
private long startTime;
public DelayObject(String data, long delay) {
this.data = data;
this.startTime = System.currentTimeMillis() + delay;
}
@Override
public long getDelay(TimeUnit unit) {
long diff = startTime - System.currentTimeMillis();
return unit.convert(diff, TimeUnit.MILLISECONDS);
}
@Override
public int compareTo(Delayed o) {
if (this.startTime < ((DelayObject) o).startTime) {
return -1;
}
if (this.startTime > ((DelayObject) o).startTime) {
return 1;
}
return 0;
}
@Override
public String toString() {
return "{" +
"data='" + data + ''' +
", startTime=" + startTime +
'}';
}
}运行此示例将为您提供以下输出：
Put object = {data='dfe77bb9-b2b4-41d2-8b32-30b3eadae4d0', startTime=1347895148107}
Put object = {data='8f7881b3-fc0d-4c4d-b7e5-e0c2db126fc6', startTime=1347895142511}
Put object = {data='c8aa530b-38bf-4045-bcfa-5917f04bebab', startTime=1347895143447}
Put object = {data='7cc45157-2f10-4f19-8758-b43b47339fb0', startTime=1347895142971}
Put object = {data='d286bdf0-10d2-4371-8b85-1a830146d500', startTime=1347895150111}
Put object = {data='e1e100e7-4aee-44e2-b41b-92f0e1eacbc1', startTime=1347895145007}
[Consumer Thread-2] - Take object = {data='8f7881b3-fc0d-4c4d-b7e5-e0c2db126fc6', startTime=1347895142511}
Put object = {data='a2bba93c-9a9e-404f-ac57-7429c3ee0798', startTime=1347895149480}
[Consumer Thread-1] - Take object = {data='7cc45157-2f10-4f19-8758-b43b47339fb0', startTime=1347895142971}
Put object = {data='bfb74a00-d93a-43dd-b777-5f563657948a', startTime=1347895144808}