Java中的阻塞隊(duì)列BlockingQueue使用詳解
1.BlockingQueue 簡(jiǎn)介
BlockingQuene是一個(gè)阻塞隊(duì)列接口,當(dāng)BlockingQueue操作無(wú)法立即響應(yīng)時(shí),有四種處理方式:
- 拋出異常;
- 返回特定的值,根據(jù)操作不同,可能是null或者false中的一個(gè);
- 無(wú)限制的阻塞當(dāng)前線程,直到操作可以成功為止;
- 根據(jù)阻塞超時(shí)設(shè)置來(lái)進(jìn)行阻塞;
BlockingQueue的核心和未響應(yīng)處理方式的對(duì)應(yīng)形式如下:
| 方式 | 拋出異常 | 返回特定值 | 無(wú)限阻塞 | 超時(shí) |
| 插入 | add(e) | offer (e) | put(e) | offer(e,time,unit) |
| 移除 | remove() | poll() | take() | poll(time,unit) |
| 查詢 | element() | peek() |
2.ArrayBlockingQueue(有界隊(duì)列)
ArrayBlockingQueue是基于數(shù)組實(shí)現(xiàn)的有界BlockingQueue,該隊(duì)列滿足先入先出(FIFO)的特性,當(dāng)隊(duì)列滿時(shí),存數(shù)據(jù)的操作會(huì)被阻塞;隊(duì)列空的時(shí)候,取數(shù)據(jù)的操作會(huì)被阻塞。
/**
* @Author Dominick Li
* @CreateTime 2022/3/6 20:03
* @Description 消息生產(chǎn)者
**/
public class Product implements Runnable {
private BlockingQueue<String> bq;
/**
* 多少秒生產(chǎn)一條任務(wù)
*/
private int period;
private Random r = new Random();
/**
* 生產(chǎn)者名稱
*/
private String name;
Product(BlockingQueue<String> bq, int period, String name) {
this.bq = bq;
this.period=period;
this.name=name;
}
@Override
public void run() {
try {
while (true){
Thread.sleep(period);
String product=String.valueOf(r.nextInt(100));
//如果隊(duì)列滿了則阻塞
bq.put(product);
System.out.println("生產(chǎn)者["+this.name+"]生產(chǎn)"+product+",當(dāng)前隊(duì)列中產(chǎn)品為:"+bq);
}
}catch (Exception e){
e.printStackTrace();
}
}
}
/**
* @Author Dominick Li
* @CreateTime 2022/3/6 20:11
* @Description 消費(fèi)者
**/
public class Cusumer implements Runnable {
private BlockingQueue<String> bq;
/**
* 多少秒獲取一條任務(wù)
*/
private int period;
/**
* 消費(fèi)者名稱
*/
private String name;
Cusumer(BlockingQueue<String> bq, int period, String name) {
this.bq = bq;
this.period=period;
this.name=name;
}
@Override
public void run() {
try {
while (true){
Thread.sleep(period);
String value=bq.take();
System.out.println("消費(fèi)者["+this.name+"]消費(fèi)"+value+",當(dāng)前隊(duì)列中產(chǎn)品為:"+bq);
}
}catch (Exception e){
e.printStackTrace();
}
}
}
public class Test {
public static void main(String[] args) {
BlockingQueue blockingQueue = new ArrayBlockingQueue(5);
ExecutorService pool = Executors.newCachedThreadPool();
pool.execute(new Product(blockingQueue, 1000, "生產(chǎn)者"));
pool.execute(new Cusumer(blockingQueue, 5000, "消費(fèi)者001"));
pool.execute(new Cusumer(blockingQueue, 5000, "消費(fèi)者002"));
pool.shutdown();
}
}
運(yùn)行效果如下

3.LinkedBlockingQueue(雙鎖線程安全隊(duì)列)
與ArrayBlockingQueue相比,LinkedBlockingQueue的重入鎖被分成了兩份,分別對(duì)應(yīng)存值和取值,這種實(shí)現(xiàn)方法被稱為雙鎖隊(duì)列算法,這樣的好處是讀寫操作的lock操作由兩個(gè)鎖控制,因此可以同時(shí)進(jìn)程讀操作和寫操作,這也是LinkedBlockingQueue吞吐量超出ArrayBlockingQueue的主要原因,但是使用兩個(gè)鎖比一個(gè)鎖復(fù)雜很多,需要考慮各種死鎖的狀態(tài)。 使用方法和ArrayBlockingQueue一致
public class Test {
public static void main(String[] args) {
LinkedBlockingQueue linkedBlockingQueue = new LinkedBlockingQueue(5);
ExecutorService pool = Executors.newCachedThreadPool();
pool.execute(new Product(linkedBlockingQueue, 1000, "生產(chǎn)者"));
pool.execute(new Cusumer(linkedBlockingQueue, 5000, "消費(fèi)者1"));
pool.shutdown();
}
}
4.PriorityBlockingQueue(優(yōu)先級(jí)隊(duì)列)
優(yōu)先級(jí)阻塞隊(duì)列ProiorityBlockQueue不是FIFO(先入先出)隊(duì)列,它要求使用者提供一個(gè)Comparetor比較器,或者隊(duì)列內(nèi)部元素實(shí)現(xiàn)Comparable接口,隊(duì)頭元素會(huì)是整個(gè)隊(duì)列里的最小元素.
PriorityBlockQueue是用數(shù)組實(shí)現(xiàn)的最小堆結(jié)構(gòu),利用的原理是: 在數(shù)組實(shí)現(xiàn)的完全二叉樹中根節(jié)點(diǎn)的下標(biāo)為子節(jié)點(diǎn)的下標(biāo)除以2,長(zhǎng)度是不定的,會(huì)隨著數(shù)據(jù)的增長(zhǎng)而逐步擴(kuò)容
public class PriorityProduct implements Comparable<PriorityProduct> {
/**
* 任務(wù)的優(yōu)先級(jí)
*/
private int priority;
private String productName;
public PriorityProduct(int priority, String productName) {
this.priority = priority;
this.productName = productName;
}
@Override
public int compareTo(PriorityProduct o) {
if (o == null) return -1;
if (o == this) return 0;
return o.priority - this.priority;
}
@Override
public String toString(){
return "{priority="+priority+",name="+this.productName;
}
}
public class PriorityBlockQueueProduct implements Runnable {
private PriorityBlockingQueue<PriorityProduct> bq;
/**
* 多少秒生產(chǎn)一條任務(wù)
*/
private int period;
private Random r = new Random();
public PriorityBlockQueueProduct(PriorityBlockingQueue<PriorityProduct> bq, int period) {
this.bq = bq;
this.period = period;
}
@Override
public void run() {
try {
while (true) {
Thread.sleep(period);
if(bq.size()>10){
//限制大小
continue;
}
//隨機(jī)生成優(yōu)先級(jí)5以內(nèi)的
PriorityProduct priorityProduct = new PriorityProduct(r.nextInt(5), "test");
//如果隊(duì)列滿了則阻塞
bq.put(priorityProduct);
//System.out.println("生產(chǎn)者商品[" +priorityProduct + "],當(dāng)前隊(duì)列中產(chǎn)品為:" + bq);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public class PriorityBlockQueueCusumer implements Runnable {
private PriorityBlockingQueue<PriorityProduct> bq;
/**
* 多少秒消費(fèi)一條任務(wù)
*/
private int period;
public PriorityBlockQueueCusumer(PriorityBlockingQueue<PriorityProduct> bq, int period) {
this.bq = bq;
this.period = period;
}
@Override
public void run() {
try {
while (true) {
Thread.sleep(period);
//如果隊(duì)列滿了則阻塞
PriorityProduct priorityProduct=bq.take();
System.out.println("消費(fèi)產(chǎn)品[" +priorityProduct + "],當(dāng)前隊(duì)列中產(chǎn)品為:" + bq);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public class PriorityTest {
public static void main(String[] args) {
PriorityBlockingQueue<PriorityProduct> priorityProducts=new PriorityBlockingQueue<>();
ExecutorService executorService= Executors.newFixedThreadPool(2);
executorService.execute(new PriorityBlockQueueProduct(priorityProducts,100));
executorService.execute(new PriorityBlockQueueCusumer(priorityProducts,1000));
}
}
運(yùn)行結(jié)果如下,可以查看消費(fèi)者在消費(fèi)的時(shí)候只會(huì)消費(fèi)任務(wù)隊(duì)列中優(yōu)先級(jí)最高的任務(wù)

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