PriorityBlockingQueue优先级规则

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PriorityBlockingQueue里面存储的对象必须是实现Comparable接口。队列通过这个接口的compare方法确定对象的priority。

规则是：当前和其他对象比较，如果compare方法返回负数，那么在队列里面的优先级就比较搞。

下面的测试可以说明这个断言：

查看打印结果，比较take出来的Entity和left的entity，比较他们的priority

public class TestPriorityQueue {static Random r=new Random(47);public static void main(String args[]){final PriorityBlockingQueue q=new PriorityBlockingQueue();ExecutorService se=Executors.newCachedThreadPool();//execute producerse.execute(new Runnable(){public void run() {int i=0;while(true){q.put(new PriorityEntity(r.nextInt(10),i++));try {TimeUnit.MILLISECONDS.sleep(r.nextInt(1000));} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}});//execute consumerse.execute(new Runnable(){public void run() {while(true){try {out.println("take-- "+q.take()+" left:-- ["+q.toString()+"]");try {TimeUnit.MILLISECONDS.sleep(r.nextInt(1000));} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}} catch (InterruptedException e) {e.printStackTrace();}}}});try {TimeUnit.SECONDS.sleep(5);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}out.println("shutdown");}}class PriorityEntity implements Comparable<PriorityEntity> {private static int count=0;private int id=count++;private int priority;private int index=0;public PriorityEntity(int _priority,int _index) {this.priority = _priority;this.index=_index;}public String toString(){return id+"# [index="+index+" priority="+priority+"]";}//数字小，优先级高public int compareTo(PriorityEntity o) {return this.priority > o.priority ? 1: this.priority < o.priority ? -1 : 0;}//数字大，优先级高//public int compareTo(PriorityTask o) {//return this.priority < o.priority ? 1//: this.priority > o.priority ? -1 : 0;//}}

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