J.U.C之AQS AQSJ.U.C之AQS，底层由线程队列实现。AbstractQueuedSynchronizer简称AQS，JUC的核心。使用Node实现FIFO队列，可以用于构建锁或者其他同步装置的基础框架。利用了一个int类型表示状态。使用方法是继承。子类通过继承并通过实现它的方法管理其状态{acquire和release}的方法操纵状态。可以同时实现排它锁和共享锁模式（独占、共享）。AQS主要同步组件CountDownLatchSemaphoreCyclicBarrierReentrantLockConditionFutureTask依次介绍1、CountDownLatch-闭锁可以完成类似阻塞的功能。一个线程或多个线程等待，直到其它线程完成。使用场景，程序执行需要某个条件执行完后，才执行。示例一package com.yanxizhu.demo.concurrency.aqs; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * @description: CountDownLatch,实现线程阻塞，等待执行完再执行程序打印 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 20:24 * @version: 1.0 */ @Slf4j @ThreadSafety public class CountDownLatchDemo { private static final int threadNum = 500; public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); CountDownLatch countDownLatch = new CountDownLatch(threadNum); for (int i = 0; i <threadNum; i++) { final int num = i; executorService.execute(() -> { try{ pringNum(num); }catch (Exception e){ log.error("执行错误【{}】", e.getMessage()); }finally { countDownLatch.countDown(); } }); } countDownLatch.await(); executorService.shutdown(); log.info("finash .."); } public static void pringNum(int num) throws InterruptedException { Thread.sleep(100); log.info("num=【{}】", num); Thread.sleep(100); } }输出结果：。。。。。 20:36:34.598 [pool-1-thread-249] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【248】 20:36:34.608 [pool-1-thread-259] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【258】 20:36:34.597 [pool-1-thread-237] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【236】 20:36:34.597 [pool-1-thread-206] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【205】 20:36:34.608 [pool-1-thread-256] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【255】 20:36:34.608 [pool-1-thread-258] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【257】 20:36:34.597 [pool-1-thread-240] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【239】 20:36:34.597 [pool-1-thread-67] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【66】 20:36:34.608 [pool-1-thread-251] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【250】 20:36:34.608 [pool-1-thread-257] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【256】 20:36:34.608 [pool-1-thread-44] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【43】 20:36:34.598 [pool-1-thread-61] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【60】 20:36:34.598 [pool-1-thread-33] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【32】 20:36:34.597 [pool-1-thread-172] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【171】 20:36:34.608 [pool-1-thread-230] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【229】 20:36:34.608 [pool-1-thread-253] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【252】 20:36:34.598 [pool-1-thread-59] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【58】 20:36:34.598 [pool-1-thread-39] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【38】 20:36:34.608 [pool-1-thread-298] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【297】 20:36:34.596 [pool-1-thread-192] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【191】 20:36:34.597 [pool-1-thread-75] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【74】 20:36:34.608 [pool-1-thread-299] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【298】 20:36:34.597 [pool-1-thread-146] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【145】 20:36:34.608 [pool-1-thread-304] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【303】 20:36:34.598 [pool-1-thread-229] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【228】 20:36:34.597 [pool-1-thread-87] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【86】 20:36:34.597 [pool-1-thread-46] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - num=【45】 20:36:34.764 [main] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo - finash ..另一种用法，给定时间内未执行执行await方法。到时间等当前线程执行完成后就不执行了。示例一package com.yanxizhu.demo.concurrency.aqs; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; /** * @description: CountDownLatch,设置等待时间 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 20:24 * @version: 1.0 */ @Slf4j @ThreadSafety public class CountDownLatchDemo2 { private static final int threadNum = 500; public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); CountDownLatch countDownLatch = new CountDownLatch(threadNum); for (int i = 0; i <threadNum; i++) { final int num = i; executorService.execute(() -> { try{ pringNum(num); }catch (Exception e){ log.error("执行错误【{}】", e.getMessage()); }finally { countDownLatch.countDown(); } }); } //设置了等待时间 countDownLatch.await(100, TimeUnit.MILLISECONDS); executorService.shutdown(); log.info("finash .."); } public static void pringNum(int num) throws InterruptedException { Thread.sleep(100); log.info("num=【{}】", num); } }输出结果20:39:27.285 [pool-1-thread-258] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【257】 20:39:27.284 [pool-1-thread-180] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【179】 20:39:27.287 [pool-1-thread-54] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【53】 20:39:27.283 [pool-1-thread-368] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【367】 20:39:27.285 [pool-1-thread-8] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【7】 20:39:27.301 [main] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - finash .. 20:39:27.286 [pool-1-thread-204] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【203】 20:39:27.301 [pool-1-thread-42] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【41】 20:39:27.305 [pool-1-thread-432] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【431】 20:39:27.285 [pool-1-thread-270] INFO com.yanxizhu.demo.concurrency.aqs.CountDownLatchDemo2 - num=【269】100毫秒后执行打印finash，之后的线程执行完后不再执行。2、Semaphore-信号量用于控制线程并发的个数。使用场景，提供仅限使用的资源。比如：有大量请求时，可用信号量控制数据库连接数，防止大量请求。示例一package com.yanxizhu.demo.concurrency.aqs; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.*; /** * @description: Semaphore-信号量，控制线程并发数 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 20:41 * @version: 1.0 */ @Slf4j @ThreadSafety public class SemaphoreDemo { private static final int threadNum = 20; private static final int currentThreadNum = 3; public static void main(String[] args) throws InterruptedException { //线程池 ExecutorService executorService = Executors.newCachedThreadPool(); //信号量 Semaphore semaphore = new Semaphore(currentThreadNum); for (int i = 0; i <threadNum; i++) { final int num = i; executorService.execute(() -> { try{ //获取一个许可 semaphore.acquire(); pringNum(num); //释放一个许可 semaphore.release(); }catch (Exception e){ log.error("执行错误【{}】", e.getMessage()); } }); } executorService.shutdown(); } public static void pringNum(int num) throws InterruptedException { log.info("num=【{}】", num); Thread.sleep(1000); } }输出结果："C:\Program Files\jdk-11.0.10_windows-x64_bin\jdk-11.0.10\bin\java.exe" -Dvisualvm.id=83604261825100 "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2020.3.2\lib\idea_rt.jar=11416:C:\Program Files\JetBrains\IntelliJ IDEA 2020.3.2\bin" -Dfile.encoding=UTF-8 -classpath D:\Workspaces\ThreadConcurrency\demo-concurrency\target\classes;D:\Tools\repo\org\springframework\boot\spring-boot-starter-web\2.6.6\spring-boot-starter-web-2.6.6.jar;D:\Tools\repo\org\springframework\boot\spring-boot-starter\2.6.6\spring-boot-starter-2.6.6.jar;D:\Tools\repo\org\springframework\boot\spring-boot-starter-logging\2.6.6\spring-boot-starter-logging-2.6.6.jar;D:\Tools\repo\ch\qos\logback\logback-classic\1.2.11\logback-classic-1.2.11.jar;D:\Tools\repo\ch\qos\logback\logback-core\1.2.11\logback-core-1.2.11.jar;D:\Tools\repo\org\apache\logging\log4j\log4j-to-slf4j\2.17.2\log4j-to-slf4j-2.17.2.jar;D:\Tools\repo\org\apache\logging\log4j\log4j-api\2.17.2\log4j-api-2.17.2.jar;D:\Tools\repo\org\slf4j\jul-to-slf4j\1.7.36\jul-to-slf4j-1.7.36.jar;D:\Tools\repo\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;D:\Tools\repo\org\yaml\snakeyaml\1.29\snakeyaml-1.29.jar;D:\Tools\repo\org\springframework\boot\spring-boot-starter-json\2.6.6\spring-boot-starter-json-2.6.6.jar;D:\Tools\repo\com\fasterxml\jackson\core\jackson-databind\2.13.2.2\jackson-databind-2.13.2.2.jar;D:\Tools\repo\com\fasterxml\jackson\core\jackson-annotations\2.13.2\jackson-annotations-2.13.2.jar;D:\Tools\repo\com\fasterxml\jackson\core\jackson-core\2.13.2\jackson-core-2.13.2.jar;D:\Tools\repo\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.13.2\jackson-datatype-jdk8-2.13.2.jar;D:\Tools\repo\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.13.2\jackson-datatype-jsr310-2.13.2.jar;D:\Tools\repo\com\fasterxml\jackson\module\jackson-module-parameter-names\2.13.2\jackson-module-parameter-names-2.13.2.jar;D:\Tools\repo\org\springframework\boot\spring-boot-starter-tomcat\2.6.6\spring-boot-starter-tomcat-2.6.6.jar;D:\Tools\repo\org\apache\tomcat\embed\tomcat-embed-core\9.0.60\tomcat-embed-core-9.0.60.jar;D:\Tools\repo\org\apache\tomcat\embed\tomcat-embed-el\9.0.60\tomcat-embed-el-9.0.60.jar;D:\Tools\repo\org\apache\tomcat\embed\tomcat-embed-websocket\9.0.60\tomcat-embed-websocket-9.0.60.jar;D:\Tools\repo\org\springframework\spring-web\5.3.18\spring-web-5.3.18.jar;D:\Tools\repo\org\springframework\spring-beans\5.3.18\spring-beans-5.3.18.jar;D:\Tools\repo\org\springframework\spring-webmvc\5.3.18\spring-webmvc-5.3.18.jar;D:\Tools\repo\org\springframework\spring-aop\5.3.18\spring-aop-5.3.18.jar;D:\Tools\repo\org\springframework\spring-context\5.3.18\spring-context-5.3.18.jar;D:\Tools\repo\org\springframework\spring-expression\5.3.18\spring-expression-5.3.18.jar;D:\Tools\repo\org\springframework\boot\spring-boot-devtools\2.6.6\spring-boot-devtools-2.6.6.jar;D:\Tools\repo\org\springframework\boot\spring-boot\2.6.6\spring-boot-2.6.6.jar;D:\Tools\repo\org\springframework\boot\spring-boot-autoconfigure\2.6.6\spring-boot-autoconfigure-2.6.6.jar;D:\Tools\repo\org\projectlombok\lombok\1.18.22\lombok-1.18.22.jar;D:\Tools\repo\org\slf4j\slf4j-api\1.7.36\slf4j-api-1.7.36.jar;D:\Tools\repo\org\springframework\spring-core\5.3.18\spring-core-5.3.18.jar;D:\Tools\repo\org\springframework\spring-jcl\5.3.18\spring-jcl-5.3.18.jar;D:\Tools\repo\com\google\guava\guava\31.1-jre\guava-31.1-jre.jar;D:\Tools\repo\com\google\guava\failureaccess\1.0.1\failureaccess-1.0.1.jar;D:\Tools\repo\com\google\guava\listenablefuture\9999.0-empty-to-avoid-conflict-with-guava\listenablefuture-9999.0-empty-to-avoid-conflict-with-guava.jar;D:\Tools\repo\com\google\code\findbugs\jsr305\3.0.2\jsr305-3.0.2.jar;D:\Tools\repo\org\checkerframework\checker-qual\3.12.0\checker-qual-3.12.0.jar;D:\Tools\repo\com\google\errorprone\error_prone_annotations\2.11.0\error_prone_annotations-2.11.0.jar;D:\Tools\repo\com\google\j2objc\j2objc-annotations\1.3\j2objc-annotations-1.3.jar;D:\Tools\repo\joda-time\joda-time\2.9.9\joda-time-2.9.9.jar com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo 20:53:22.696 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【1】 20:53:22.696 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【2】 20:53:22.696 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【0】 20:53:23.707 [pool-1-thread-5] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【4】 20:53:23.707 [pool-1-thread-6] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【5】 20:53:23.707 [pool-1-thread-7] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【6】 20:53:24.711 [pool-1-thread-13] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【12】 20:53:24.711 [pool-1-thread-8] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【7】 20:53:24.711 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【3】 20:53:25.726 [pool-1-thread-9] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【8】 20:53:25.726 [pool-1-thread-12] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【11】 20:53:25.726 [pool-1-thread-14] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【13】 20:53:26.738 [pool-1-thread-16] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【15】 20:53:26.738 [pool-1-thread-11] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【10】 20:53:26.738 [pool-1-thread-10] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【9】 20:53:27.741 [pool-1-thread-18] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【17】 20:53:27.741 [pool-1-thread-17] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【16】 20:53:27.741 [pool-1-thread-15] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【14】 20:53:28.741 [pool-1-thread-19] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【18】 20:53:28.741 [pool-1-thread-20] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo - num=【19】 Process finished with exit code 0通过结果可以看到，每秒只打印2个数字，就是信号量控制的。示例二同时获取多个许可，释放多个许可，也可以一个一个释放许可。下面代码示例，只有2个并发线程所有，获取后没有了，就类似单线程。package com.yanxizhu.demo.concurrency.aqs; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; /** * @description: Semaphore-信号量，控制线程并发数，可以获取或释放多个许可 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 20:41 * @version: 1.0 */ @Slf4j @ThreadSafety public class SemaphoreDemo2 { private static final int threadNum = 20; private static final int currentThreadNum = 3; public static void main(String[] args) throws InterruptedException { //线程池 ExecutorService executorService = Executors.newCachedThreadPool(); //信号量 Semaphore semaphore = new Semaphore(currentThreadNum); for (int i = 0; i <threadNum; i++) { final int num = i; executorService.execute(() -> { try{ //获取3个许可，需要等3个都执行完了，才释放3个许可 semaphore.acquire(3); pringNum(num); //释放3个许可 semaphore.release(3); }catch (Exception e){ log.error("执行错误【{}】", e.getMessage()); } }); } executorService.shutdown(); } public static void pringNum(int num) throws InterruptedException { log.info("num=【{}】", num); Thread.sleep(1000); } }输出结果：20:56:17.733 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【0】 20:56:18.740 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【1】 20:56:19.754 [pool-1-thread-6] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【5】 20:56:20.755 [pool-1-thread-7] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【6】 20:56:21.767 [pool-1-thread-10] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【9】 20:56:22.780 [pool-1-thread-8] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【7】 20:56:23.791 [pool-1-thread-5] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【4】 20:56:24.800 [pool-1-thread-9] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【8】 20:56:25.801 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【3】 20:56:26.812 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【2】 20:56:27.824 [pool-1-thread-11] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【10】 20:56:28.834 [pool-1-thread-12] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【11】 20:56:29.847 [pool-1-thread-13] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【12】 20:56:30.850 [pool-1-thread-14] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【13】 20:56:31.853 [pool-1-thread-17] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【16】 20:56:32.863 [pool-1-thread-15] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【14】 20:56:33.873 [pool-1-thread-16] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【15】 20:56:34.885 [pool-1-thread-18] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【17】 20:56:35.885 [pool-1-thread-19] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【18】 20:56:36.897 [pool-1-thread-20] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo2 - num=【19】 Disconnected from the target VM, address: '127.0.0.1:13050', transport: 'socket'示例三当线程数超过并发数，就丢失多余的。package com.yanxizhu.demo.concurrency.aqs; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; /** * @description: Semaphore-信号量，控制线程并发数，超过并发量时掉漆多余线程 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 20:41 * @version: 1.0 */ @Slf4j @ThreadSafety public class SemaphoreDemo3 { private static final int threadNum = 20; private static final int currentThreadNum = 3; public static void main(String[] args) throws InterruptedException { //线程池 ExecutorService executorService = Executors.newCachedThreadPool(); //信号量 Semaphore semaphore = new Semaphore(currentThreadNum); for (int i = 0; i <threadNum; i++) { final int num = i; executorService.execute(() -> { try{ //尝试获取许可，获取到才执行 if (semaphore.tryAcquire()) { pringNum(num); //释放一个许可 semaphore.release(); } }catch (Exception e){ log.error("执行错误【{}】", e.getMessage()); } }); } executorService.shutdown(); } public static void pringNum(int num) throws InterruptedException { log.info("num=【{}】", num); Thread.sleep(1000); } }输出结果：21:04:48.376 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo3 - num=【0】 21:04:49.387 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo3 - num=【1】 Disconnected from the target VM, address: '127.0.0.1:2839', transport: 'socket'只输出2个线程，其它18个线程被丢弃。tryAcquire方法重载说明：//无参 public boolean tryAcquire() { return sync.nonfairTryAcquireShared(1) >= 0; } //1个参数，获取许可个数 public boolean tryAcquire(int permits) { if (permits < 0) throw new IllegalArgumentException(); return sync.nonfairTryAcquireShared(permits) >= 0; } //2个参数，超时时间，单位 public boolean tryAcquire(long timeout, TimeUnit unit) throws InterruptedException { return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout)); } //3个参数，获取许可个数，超时时间，单位 public boolean tryAcquire(int permits, long timeout, TimeUnit unit) throws InterruptedException { if (permits < 0) throw new IllegalArgumentException(); return sync.tryAcquireSharedNanos(permits, unit.toNanos(timeout)); }示例四设置超时时间package com.yanxizhu.demo.concurrency.aqs; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; import java.util.concurrent.TimeUnit; /** * @description: Semaphore-信号量，控制线程并发数，带超时时间限制的 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 20:41 * @version: 1.0 */ @Slf4j @ThreadSafety public class SemaphoreDemo4 { private static final int threadNum = 50; private static final int currentThreadNum = 3; public static void main(String[] args) throws InterruptedException { //线程池 ExecutorService executorService = Executors.newCachedThreadPool(); //信号量 Semaphore semaphore = new Semaphore(currentThreadNum); for (int i = 0; i <threadNum; i++) { final int num = i; executorService.execute(() -> { try{ //尝试获取许可，获取到才执行，获取超过3秒，就不执行了。 if (semaphore.tryAcquire(3000, TimeUnit.MILLISECONDS)) { pringNum(num); //释放一个许可 semaphore.release(); } }catch (Exception e){ log.error("执行错误【{}】", e.getMessage()); } }); } executorService.shutdown(); } public static void pringNum(int num) throws InterruptedException { log.info("num=【{}】", num); Thread.sleep(1000); } }输出结果：22:01:36.804 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【0】 22:01:36.804 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【2】 22:01:36.804 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【1】 22:01:37.828 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【3】 22:01:37.828 [pool-1-thread-6] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【5】 22:01:37.828 [pool-1-thread-10] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【9】 22:01:38.843 [pool-1-thread-12] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【11】 22:01:38.843 [pool-1-thread-13] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【12】 22:01:38.843 [pool-1-thread-8] INFO com.yanxizhu.demo.concurrency.aqs.SemaphoreDemo4 - num=【7】 Disconnected from the target VM, address: '127.0.0.1:11385', transport: 'socket'3、CyclicBarrier允许一组线程相互等待，直到达到某个共同屏障点，直到每个线程都就绪后面的才继续往下执行。和CoutDownLatch相似都是通过计数器来实现的，图从下往上看的。线程释放后可以循环使用，因此也叫循环屏障。CoutDownLatch用户分计算，汇总最后的结果。示例一package com.yanxizhu.demo.concurrency.aqs; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.BrokenBarrierException; import java.util.concurrent.CyclicBarrier; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * @description: CyclicBarrier 实现线程相互等待 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 22:15 * @version: 1.0 */ @Slf4j public class CyclicBarrierDemo { //定义需要相互等待5个线程，就绪后才执行，后面的代码 private static final CyclicBarrier cyclicBarrier = new CyclicBarrier(4); public static void main(String[] args) throws Exception{ //线程池 ExecutorService executorService = Executors.newCachedThreadPool(); for (int i = 0; i < 10; i++) { final int threadNum = i; //模式看效果，等待1秒 Thread.sleep(1000); executorService.execute(() -> { try { pringWait(threadNum); } catch (Exception e) { log.error("执行出错了。。。", e.getMessage()); } }); } executorService.shutdown(); } public static void pringWait(int threadNum) throws InterruptedException, BrokenBarrierException { //模式看效果，等待1秒 Thread.sleep(1000); log.info("等待中。。。{}", threadNum); //告诉线程每个就绪了，await方法支持传入超时时间 //可选参数long timeout, TimeUnit unit cyclicBarrier.await(); //就绪后才执行 log.info("开始执行了。。{}",threadNum); } }输出结果：Connected to the target VM, address: '127.0.0.1:14410', transport: 'socket' 22:26:04.855 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。0 22:26:05.853 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。1 22:26:06.866 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。2 22:26:07.881 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。3 22:26:07.881 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。3 22:26:07.882 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。1 22:26:07.882 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。2 22:26:07.881 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。0 22:26:08.896 [pool-1-thread-5] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。4 22:26:09.899 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。5 22:26:10.901 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。6 22:26:11.902 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。7 22:26:11.902 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。7 22:26:11.902 [pool-1-thread-5] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。4 22:26:11.902 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。6 22:26:11.902 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 开始执行了。。5 22:26:12.903 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。8 22:26:13.916 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo - 等待中。。。9 Disconnected from the target VM, address: '127.0.0.1:14410', transport: 'socket'示例二带超时时间的，注意需要trycatch才能不影响后续流程执行。package com.yanxizhu.demo.concurrency.aqs; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.*; /** * @description: CyclicBarrier 实现线程相互等待,带超时时间，注意捕获异常，才能继续执行后面的操作 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 22:15 * @version: 1.0 */ @Slf4j public class CyclicBarrierDemo2 { //定义需要相互等待5个线程，就绪后才执行，后面的代码 private static final CyclicBarrier cyclicBarrier = new CyclicBarrier(4); public static void main(String[] args) throws Exception{ //线程池 ExecutorService executorService = Executors.newCachedThreadPool(); for (int i = 0; i < 10; i++) { final int threadNum = i; //模式看效果，等待1秒 Thread.sleep(1000); executorService.execute(() -> { try { pringWait(threadNum); } catch (Exception e) { log.error("执行出错了。。。", e.getMessage()); } }); } executorService.shutdown(); } public static void pringWait(int threadNum) throws InterruptedException, BrokenBarrierException { //模式看效果，等待1秒 Thread.sleep(1000); log.info("等待中。。。{}", threadNum); //告诉线程每个就绪了，带超时时间 try { cyclicBarrier.await(2000, TimeUnit.MILLISECONDS); } catch (Exception e){ log.warn("超时了，注意：捕获异常，才能继续执行", e.getMessage()); } //就绪后才执行 log.info("开始执行了。。{}",threadNum); } }输出结果：22:37:57.786 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。0 22:37:58.797 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。1 22:37:59.797 [pool-1-thread-1] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:37:59.797 [pool-1-thread-2] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:37:59.797 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。0 22:37:59.798 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。1 22:37:59.812 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。2 22:37:59.812 [pool-1-thread-3] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:37:59.812 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。2 22:38:00.813 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。3 22:38:00.813 [pool-1-thread-1] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:38:00.813 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。3 22:38:01.828 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。4 22:38:01.828 [pool-1-thread-3] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:38:01.828 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。4 22:38:02.840 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。5 22:38:02.840 [pool-1-thread-1] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:38:02.840 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。5 22:38:03.842 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。6 22:38:03.842 [pool-1-thread-3] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:38:03.842 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。6 22:38:04.855 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。7 22:38:04.855 [pool-1-thread-1] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:38:04.855 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。7 22:38:05.870 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。8 22:38:05.870 [pool-1-thread-3] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:38:05.870 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。8 22:38:06.870 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 等待中。。。9 22:38:06.870 [pool-1-thread-1] WARN com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 超时了，注意：捕获异常，才能继续执行 22:38:06.870 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo2 - 开始执行了。。9 Disconnected from the target VM, address: '127.0.0.1:2195', transport: 'socket'示例三构造可以传入runable线程，优先执行。package com.yanxizhu.demo.concurrency.aqs; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.BrokenBarrierException; import java.util.concurrent.CyclicBarrier; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * @description: CyclicBarrier 实现线程相互等待，CyclicBarrier可以传入runable线程，优先执行该部分代码 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/25 22:15 * @version: 1.0 */ @Slf4j public class CyclicBarrierDemo3 { //定义需要相互等待5个线程，就绪后才执行，后面的代码 private static final CyclicBarrier cyclicBarrier = new CyclicBarrier(4, () -> { log.info("相互等待线程都就绪后，这部分代码先执行"); }); public static void main(String[] args) throws Exception{ //线程池 ExecutorService executorService = Executors.newCachedThreadPool(); for (int i = 0; i < 10; i++) { final int threadNum = i; //模式看效果，等待1秒 Thread.sleep(1000); executorService.execute(() -> { try { pringWait(threadNum); } catch (Exception e) { log.error("执行出错了。。。", e.getMessage()); } }); } executorService.shutdown(); } public static void pringWait(int threadNum) throws InterruptedException, BrokenBarrierException { //模式看效果，等待1秒 Thread.sleep(1000); log.info("等待中。。。{}", threadNum); //告诉线程每个就绪了，await方法支持传入超时时间 //可选参数long timeout, TimeUnit unit cyclicBarrier.await(); //就绪后才执行 log.info("开始执行了。。{}",threadNum); } }输出结果：22:42:09.313 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。0 22:42:10.313 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。1 22:42:11.318 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。2 22:42:12.320 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。3 22:42:12.320 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 相互等待线程都就绪后，这部分代码先执行 22:42:12.320 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。3 22:42:12.320 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。2 22:42:12.320 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。1 22:42:12.320 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。0 22:42:13.325 [pool-1-thread-5] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。4 22:42:14.339 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。5 22:42:15.353 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。6 22:42:16.355 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。7 22:42:16.355 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 相互等待线程都就绪后，这部分代码先执行 22:42:16.355 [pool-1-thread-1] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。7 22:42:16.355 [pool-1-thread-5] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。4 22:42:16.355 [pool-1-thread-3] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。5 22:42:16.355 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 开始执行了。。6 22:42:17.358 [pool-1-thread-4] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。8 22:42:18.372 [pool-1-thread-2] INFO com.yanxizhu.demo.concurrency.aqs.CyclicBarrierDemo3 - 等待中。。。9总结：注意CoutDownLatch与CyclicBarrier的不同，对别使用。

原子性-Atomic类常见的使用 1、(信号量)Semaphore+(闭锁)CountDownLatch+(常用源自类)AtomicIntegerpackage com.yanxizhu.demo.concurrency.atomic; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; import java.util.concurrent.atomic.AtomicInteger; /** * @description: 线程安全 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/19 20:05 * @version: 1.0 */ @Slf4j @ThreadSafety public class DemoSemaphoreAndCountDownLatchAndAtomic { //用户数量 private static final int clientsTotal = 5000; //并发数量 private static final int concurrencyTotal = 200; //累加总和 private static AtomicInteger count = new AtomicInteger(0); public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); //信号量 final Semaphore semaphore = new Semaphore(clientsTotal); //闭锁 final CountDownLatch countDownLatch = new CountDownLatch(concurrencyTotal); for (int i = 0; i < clientsTotal; i++) { executorService.execute(()->{ try { semaphore.acquire(); add(); semaphore.release(); } catch (InterruptedException e) { log.error("出现错误:【{}】", e.getMessage()); } countDownLatch.countDown(); }); } countDownLatch.await(); executorService.shutdown(); log.info("累加结果为count=【{}】",count.get()); } /** * 累加 */ private static void add(){ //说明:incrementAndGet、getAndIncrement类似,i++与++i count.incrementAndGet(); count.getAndIncrement(); } }运行结果：累加结果为count=【10000】2、AtomicReferencepackage com.yanxizhu.demo.concurrency.atomic; import com.yanxizhu.demo.concurrency.annotation.ThreadSafety; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.atomic.AtomicReference; /** * @description: AtomicReference * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/20 21:09 * @version: 1.0 */ @Slf4j @ThreadSafety public class DemoAtomicReference { public static AtomicReference<Integer> count = new AtomicReference<>(0); public static void main(String[] args) { count.compareAndSet(0, 2); count.compareAndSet(0, 1); count.compareAndSet(1, 3); count.compareAndSet(2, 4); count.compareAndSet(3, 5); log.info("count结果为【{}】",count.get()); } }运行结果：count结果为【4】3、AtomicIntegerFieldUpdaterpackage com.yanxizhu.demo.concurrency.atomic; import lombok.Getter; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.atomic.AtomicIntegerFieldUpdater; /** * @description: AtomicIntegerFieldUpdater,原子性修改 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/20 21:17 * @version: 1.0 */ @Slf4j public class DemoAtomicIntegerFieldUpdater { private static AtomicIntegerFieldUpdater<DemoAtomicIntegerFieldUpdater> updater = AtomicIntegerFieldUpdater.newUpdater(DemoAtomicIntegerFieldUpdater.class, "count"); @Getter public volatile int count = 100; private static DemoAtomicIntegerFieldUpdater demoAtomicIntegerFieldUpdater = new DemoAtomicIntegerFieldUpdater(); public static void main(String[] args) { if(updater.compareAndSet(demoAtomicIntegerFieldUpdater, 100, 200)) { log.info("updater succcess1,{}", demoAtomicIntegerFieldUpdater.getCount()); } if(updater.compareAndSet(demoAtomicIntegerFieldUpdater, 100, 200)) { log.info("updater succcess2,{}", demoAtomicIntegerFieldUpdater.getCount()); }else { log.info("updater fail,{}", demoAtomicIntegerFieldUpdater.getCount()); } } }运行结果：updater succcess1,200 updater fail,2004、AtomicStampedReference主要用于解决CAS中ABA问题，主要是AtomicStampedReference类中compareAndSet方法多了一个stamp的比较。stamp是每次更新来维护的。 public boolean compareAndSet(V expectedReference, V newReference, int expectedStamp, int newStamp) { Pair<V> current = pair; return expectedReference == current.reference && expectedStamp == current.stamp && ((newReference == current.reference && newStamp == current.stamp) || casPair(current, Pair.of(newReference, newStamp))); } 5、LongAdderJDK1.8后新增了LongAdder。AtomicLong：是基于 CAS 方式自旋更新的；LongAdder： 是把 value 分成若干cell，并发量低的时候，直接 CAS 更新值，成功即结束。并发量高的情况，CAS更新某个cell值和需要时对cell数据扩容，成功结束；更新失败自旋 CAS 更新 cell值。取值的时候，调用 sum() 方法进行每个cell累加。AtomicLong： 包含有原子性的读、写结合的api；LongAdder ：没有原子性的读、写结合的api，能保证结果最终一致性。低并发：低并发场景AtomicLong 和 LongAdder 性能相似。高并发：高并发场景 LongAdder 性能优于 AtomicLong。6、AtomicLongArray主要用于原子修改数组 // 下标， 期望值 更新值 public final boolean compareAndSet(int i, long expectedValue, long newValue) { return AA.compareAndSet(array, i, expectedValue, newValue); }通过传入下标、期望值、要更新的值进行修改。7、AtomicBoolean public final boolean compareAndSet(boolean expectedValue, boolean newValue) { return VALUE.compareAndSet(this, (expectedValue ? 1 : 0), (newValue ? 1 : 0)); }package com.yanxizhu.demo.concurrency.atomic; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; import java.util.concurrent.atomic.AtomicBoolean; /** * @description: 结果，最后只会执行一次 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/20 22:05 * @version: 1.0 */ @Slf4j public class DemoAtomicBoolean { private static AtomicBoolean isHappen = new AtomicBoolean(false); //用户数量 private static final int clientsTotal = 5000; //并发数量 private static final int concurrencyTotal = 200; public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); //信号量 final Semaphore semaphore = new Semaphore(clientsTotal); //闭锁 final CountDownLatch countDownLatch = new CountDownLatch(concurrencyTotal); for (int i = 0; i < clientsTotal; i++) { executorService.execute(()->{ try { semaphore.acquire(); test(); semaphore.release(); } catch (InterruptedException e) { log.error("出现错误:【{}】", e.getMessage()); } countDownLatch.countDown(); }); } countDownLatch.await(); executorService.shutdown(); log.info("isHappen结果为count=【{}】",isHappen.get()); } public static void test() { //从false变成true是一次原子操作，只会执行一次 if(isHappen.compareAndSet(false, true)) { log.info("execute .. {}", isHappen); } } }运行结果：execute .. true isHappen结果为count=【true】