JAvaマルチスレッドコンポーネント2:DelayQueueの使い方
この文章は主にDeleyQueueの使用方法を紹介するために用いられ、この種類の名前から判断することができます.これはQueueで、その中から行く要素の順序は時間の遅延によって来ています.ネット上には多くの例がありますが、あまり詳しくありません.本の例を見て、自分の考えで書いてみましたが、中にはまだ多くの誤解があることに気づきました.次のプログラムは例で、いくつかのコメントが追加されています.
/**
*
*/
package com.eric.concurrency;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
/**
* this class used to explain how to use delayqueue
* @author Eric
*
*/
public class DelayQueueDemo {
public static void main(String[] args) {
try {
ExecutorService es = Executors.newCachedThreadPool();
DelayQueue<DelayTask> queue = new DelayQueue<DelayTask>();
Random rand = new Random();
// add 20's DelayTask to DelayQueue
for (int i = 0; i < 20; i++) {
queue.add(new DelayTask(rand.nextInt(500)));
}
EndTask endTaks = new EndTask(501);
// add endtask to DelayQueue, it's time is 50001 to ensure will be
// execute at the end of queue
queue.add(endTaks);
es.execute(new DelayConsumer(queue));
TimeUnit.SECONDS.sleep(1);
es.shutdownNow();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
class DelayConsumer implements Runnable {
private DelayQueue<DelayTask> queue;
public DelayConsumer(DelayQueue<DelayTask> queue) {
this.queue = queue;
}
public void run() {
try {
System.out.println("############print order by DelayQueue###############");
// from DelayQueue get DelayTask and execute it
while (!Thread.interrupted()) {
queue.take().run();
}
} catch (InterruptedException e) {
System.out.println("Exit Consumer");
}
}
}
class EndTask extends DelayTask {
public EndTask(long delay) {
super(delay);
}
@Override
public void run() {
try {
TimeUnit.MILLISECONDS.sleep(1);
// print all task from internal list
System.out.println("#############print by list order###############");
for (DelayTask delayTask : tasks) {
System.out.println("end" + delayTask);
}
} catch (InterruptedException e) {
System.out.println("Exit LIST");
}
}
}
class DelayTask implements Runnable, Delayed {
protected static List<DelayTask> tasks = new ArrayList<DelayTask>();
public long time = 0;
public long delay;
private static int count = 0;
private int id = count++;
public DelayTask(long delay) {
this.delay = delay;
time = System.nanoTime() + TimeUnit.NANOSECONDS.convert(this.delay, TimeUnit.MICROSECONDS);
tasks.add(this);
}
@Override
public int compareTo(Delayed o) {
long result = ((DelayTask) o).getTime() - this.getTime();
if (result > 0) {
return 1;
}
if (result < 0) {
return -1;
}
return 0;
}
@Override
public long getDelay(TimeUnit unit) {
return unit.convert(time - System.nanoTime(), TimeUnit.NANOSECONDS);
}
@Override
public void run() {
System.out.println(this);
}
public String toString() {
// use time to print for get real "delay time"
return "Task " + id + ":" + time;
}
public long getTime() {
return time;
}
public void setTime(long time) {
this.time = time;
}
}