Java并发-类库新组件 - PriorityBlockingQueue 理解

直接上代码进行理解：

package com.xyw.concurrent.blog;import java.util.concurrent.*;import java.util.*;/* * 优先队列， 任务按照优先级顺序从队列中出现的任务， PrioritizedTask 被赋予一个优先级数 以此来提供这种顺序 */class PrioritizedTask implements Runnable, Comparable<PrioritizedTask>{//能放进队列的任务是实现了 Comparable 的情况private Random rand  = new Random(47);private static int counter = 0;private final int id  = counter ++; // 任务的唯一标识private final int priority;protected static List<PrioritizedTask> sequence = new ArrayList<PrioritizedTask>();public PrioritizedTask(int priority){this.priority = priority;sequence.add(this); // 用于添加创建的顺序的情况}public int compareTo(PrioritizedTask arg){ // 实现 comparable 的固定的接口return priority < arg.priority ? 1: (priority > arg.priority) ? -1 : 0;}public void run(){try{TimeUnit.MILLISECONDS.sleep(rand.nextInt(250));}catch(InterruptedException e){}System.out.println(this);}public String toString(){return String.format("[%1$-3d]", priority) + "Task" + id;}public String summary(){return "(" + id + ":" + priority + ")";}public static class EndSentinel extends PrioritizedTask{ // 内部类，用于终结的任务private ExecutorService exec;public EndSentinel(ExecutorService e){super(-1);exec = e ;}public void run(){int count  = 0;for(PrioritizedTask pt : sequence){System.out.println(pt.summary());if(++count % 5 == 0){System.out.println();}}System.out.println();System.out.println(this + "Calling shutdownNow()");exec.shutdownNow();}}}class PrioritizedTaskProducer implements Runnable{private Random rand = new Random(47);private Queue<Runnable> queue;private ExecutorService exec;public PrioritizedTaskProducer(Queue<Runnable> q, ExecutorService e){queue = q;exec = e ;}public void run(){for(int i  =0; i < 20; i++){queue.add(new PrioritizedTask(rand.nextInt(10)));// 这里面加入的是一个线程的对象//Thread.yield(); 这个地方出现了情况，如果加入了Thread.yield(); 这个函数，那么会在第一个出现非优先队列的情况}try{for(int i = 0; i < 10; i++){TimeUnit.MILLISECONDS.sleep(250);queue.add(new PrioritizedTask(10));}for(int i = 0; i < 10; i++){queue.add(new PrioritizedTask(i));}queue.add(new PrioritizedTask.EndSentinel(exec));}catch(InterruptedException e){}System.out.println("Finished PrioritizedTaskProducer");}}class PrioritizedTaskConsumer implements Runnable{private PriorityBlockingQueue<Runnable> q; // 使用了 PriorityBlockingQueue 这个队列的情况public PrioritizedTaskConsumer( PriorityBlockingQueue<Runnable> q){this.q= q;}public void run(){try{while(!Thread.interrupted()){q.take().run();}}catch(InterruptedExceptione){}System.out.println("Finished PrioritizedTaskConsumer");}}public class PriorityBlockingQueueDemo {public static void main(String[] args) throws Exception{Random rand = new Random(47);ExecutorService exec = Executors.newCachedThreadPool();PriorityBlockingQueue<Runnable>queue = new PriorityBlockingQueue<Runnable>();exec.execute(new PrioritizedTaskProducer(queue, exec)); // 任务的生产者exec.execute(new PrioritizedTaskConsumer(queue)); // 任务的消费者}}

运行结果，注意 （注释之处的 Thread.yield() ）这个加与不加与运行的结果有关

[9  ]Task5

[9  ]Task13

[9  ]Task14

[8  ]Task10

[8  ]Task15

[8  ]Task16

[8  ]Task0

[8  ]Task19

[8  ]Task11

[8  ]Task6

[7  ]Task9

[5  ]Task1

[3  ]Task2

[2  ]Task8

[1  ]Task12

[1  ]Task17

[1  ]Task4

[1  ]Task3

[0  ]Task7

[0  ]Task18

[10 ]Task20

[10 ]Task21

[10 ]Task22

[10 ]Task23

[10 ]Task24

[10 ]Task25

[10 ]Task26

[10 ]Task27

[10 ]Task28

Finished PrioritizedTaskProducer

[10 ]Task29

[9  ]Task39

[8  ]Task38

[7  ]Task37

[6  ]Task36

[5  ]Task35

[4  ]Task34

[3  ]Task33

[2  ]Task32

[1  ]Task31

[0  ]Task30

(0:8)

(1:5)

(2:3)

(3:1)

(4:1)

(5:9)

(6:8)

(7:0)

(8:2)

(9:7)

(10:8)

(11:8)

(12:1)

(13:9)

(14:9)

(15:8)

(16:8)

(17:1)

(18:0)

(19:8)

(20:10)

(21:10)

(22:10)

(23:10)

(24:10)

(25:10)

(26:10)

(27:10)

(28:10)

(29:10)

(30:0)

(31:1)

(32:2)

(33:3)

(34:4)

(35:5)

(36:6)

(37:7)

(38:8)

(39:9)

(40:-1)

[-1 ]Task40Calling shutdownNow()

Finished PrioritizedTaskConsumer