J.U.C-AQS-CyclicBarrier

允许一组线程相互等待，直到到达某个公共的屏障点

可以完成多个线程之间相互等待，只有当每个线程都准备就绪后才能各自继续执行后续的操作

与CountDownLatch的区别
1.CountDownLatch的计数器只能使用一次而CyclicBarrier的计数器可以通过reset重置
2.CountDownLatch主要是实现一个或n个线程需要等待其他线程完成某项操作后才能继续往下执行，描述的是一个或n个线程等待其他线程的关系而CyclicBarrier描述的是多个线程之间相互等待的关系

package io.haitaoc.concurrency.example.aqs;

import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class CyclicBarrierExample1 {

    private static CyclicBarrier barrier = new CyclicBarrier(5);


    public static void main(String[] args) throws InterruptedException {

        ExecutorService executorService  = Executors.newCachedThreadPool();

        for (int i = 0; i < 10; i++) {
            final int threadNum = i;
            Thread.sleep(1000);
            executorService.execute(()->{
                try {
                    race(threadNum);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        }
    }

    private static void race(int threadNum)throws Exception{
        Thread.sleep(1000);
        System.out.println(threadNum+" is ready");
        barrier.await();
        System.out.println(threadNum+" continue");
    }
}

Output:

"C:\Program Files\Java\jdk-9\bin\java" "-javaagent:C:\Users\haitaoc\IntelliJ IDEA 2018.1\lib\idea_rt.jar=7405:C:\Users\haitaoc\IntelliJ IDEA 2018.1\bin" -Dfile.encoding=UTF-8 -classpath D:\IdeaProjects\concurrency\target\classes;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-web\2.0.0.RELEASE\spring-boot-starter-web-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter\2.0.0.RELEASE\spring-boot-starter-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot\2.0.0.RELEASE\spring-boot-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-autoconfigure\2.0.0.RELEASE\spring-boot-autoconfigure-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-logging\2.0.0.RELEASE\spring-boot-starter-logging-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;C:\Users\haitaoc\.m2\repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;C:\Users\haitaoc\.m2\repository\org\slf4j\slf4j-api\1.7.25\slf4j-api-1.7.25.jar;C:\Users\haitaoc\.m2\repository\org\apache\logging\log4j\log4j-to-slf4j\2.10.0\log4j-to-slf4j-2.10.0.jar;C:\Users\haitaoc\.m2\repository\org\apache\logging\log4j\log4j-api\2.10.0\log4j-api-2.10.0.jar;C:\Users\haitaoc\.m2\repository\org\slf4j\jul-to-slf4j\1.7.25\jul-to-slf4j-1.7.25.jar;C:\Users\haitaoc\.m2\repository\javax\annotation\javax.annotation-api\1.3.2\javax.annotation-api-1.3.2.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-core\5.0.4.RELEASE\spring-core-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-jcl\5.0.4.RELEASE\spring-jcl-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\yaml\snakeyaml\1.19\snakeyaml-1.19.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-json\2.0.0.RELEASE\spring-boot-starter-json-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\core\jackson-databind\2.9.4\jackson-databind-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\core\jackson-annotations\2.9.0\jackson-annotations-2.9.0.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\core\jackson-core\2.9.4\jackson-core-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.9.4\jackson-datatype-jdk8-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.9.4\jackson-datatype-jsr310-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\module\jackson-module-parameter-names\2.9.4\jackson-module-parameter-names-2.9.4.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-tomcat\2.0.0.RELEASE\spring-boot-starter-tomcat-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\apache\tomcat\embed\tomcat-embed-core\8.5.28\tomcat-embed-core-8.5.28.jar;C:\Users\haitaoc\.m2\repository\org\apache\tomcat\embed\tomcat-embed-el\8.5.28\tomcat-embed-el-8.5.28.jar;C:\Users\haitaoc\.m2\repository\org\apache\tomcat\embed\tomcat-embed-websocket\8.5.28\tomcat-embed-websocket-8.5.28.jar;C:\Users\haitaoc\.m2\repository\org\hibernate\validator\hibernate-validator\6.0.7.Final\hibernate-validator-6.0.7.Final.jar;C:\Users\haitaoc\.m2\repository\javax\validation\validation-api\2.0.1.Final\validation-api-2.0.1.Final.jar;C:\Users\haitaoc\.m2\repository\org\jboss\logging\jboss-logging\3.3.0.Final\jboss-logging-3.3.0.Final.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\classmate\1.3.1\classmate-1.3.1.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-web\5.0.4.RELEASE\spring-web-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-beans\5.0.4.RELEASE\spring-beans-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-webmvc\5.0.4.RELEASE\spring-webmvc-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-aop\5.0.4.RELEASE\spring-aop-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-context\5.0.4.RELEASE\spring-context-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-expression\5.0.4.RELEASE\spring-expression-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\projectlombok\lombok\1.16.16\lombok-1.16.16.jar;C:\Users\haitaoc\.m2\repository\com\google\guava\guava\10.0.1\guava-10.0.1.jar;C:\Users\haitaoc\.m2\repository\com\google\code\findbugs\jsr305\1.3.9\jsr305-1.3.9.jar;C:\Users\haitaoc\.m2\repository\joda-time\joda-time\2.9.9\joda-time-2.9.9.jar io.haitaoc.concurrency.example.aqs.CyclicBarrierExample1
0 is ready
1 is ready
2 is ready
3 is ready
4 is ready
4 continue
0 continue
1 continue
2 continue
3 continue
5 is ready
6 is ready
7 is ready
8 is ready
9 is ready
9 continue
7 continue
8 continue
6 continue
5 continue

package io.haitaoc.concurrency.example.aqs;



import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


public class CyclicBarrierExample3 {

    private static CyclicBarrier barrier = new CyclicBarrier(5, () -> {
        System.out.println("callback is running");
    });

    public static void main(String[] args) throws Exception {

        ExecutorService executor = Executors.newCachedThreadPool();

        for (int i = 0; i < 10; i++) {
            final int threadNum = i;
            Thread.sleep(1000);
            executor.execute(() -> {
                try {
                    race(threadNum);
                } catch (Exception e) {
                   e.printStackTrace();
                }
            });
        }
        executor.shutdown();
    }

    private static void race(int threadNum) throws Exception {
        Thread.sleep(1000);
        System.out.println(threadNum+" is ready" );
        barrier.await();
        System.out.println(threadNum+" continue");
    }
}

Output:

"C:\Program Files\Java\jdk-9\bin\java" "-javaagent:C:\Users\haitaoc\IntelliJ IDEA 2018.1\lib\idea_rt.jar=7829:C:\Users\haitaoc\IntelliJ IDEA 2018.1\bin" -Dfile.encoding=UTF-8 -classpath D:\IdeaProjects\concurrency\target\classes;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-web\2.0.0.RELEASE\spring-boot-starter-web-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter\2.0.0.RELEASE\spring-boot-starter-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot\2.0.0.RELEASE\spring-boot-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-autoconfigure\2.0.0.RELEASE\spring-boot-autoconfigure-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-logging\2.0.0.RELEASE\spring-boot-starter-logging-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;C:\Users\haitaoc\.m2\repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;C:\Users\haitaoc\.m2\repository\org\slf4j\slf4j-api\1.7.25\slf4j-api-1.7.25.jar;C:\Users\haitaoc\.m2\repository\org\apache\logging\log4j\log4j-to-slf4j\2.10.0\log4j-to-slf4j-2.10.0.jar;C:\Users\haitaoc\.m2\repository\org\apache\logging\log4j\log4j-api\2.10.0\log4j-api-2.10.0.jar;C:\Users\haitaoc\.m2\repository\org\slf4j\jul-to-slf4j\1.7.25\jul-to-slf4j-1.7.25.jar;C:\Users\haitaoc\.m2\repository\javax\annotation\javax.annotation-api\1.3.2\javax.annotation-api-1.3.2.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-core\5.0.4.RELEASE\spring-core-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-jcl\5.0.4.RELEASE\spring-jcl-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\yaml\snakeyaml\1.19\snakeyaml-1.19.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-json\2.0.0.RELEASE\spring-boot-starter-json-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\core\jackson-databind\2.9.4\jackson-databind-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\core\jackson-annotations\2.9.0\jackson-annotations-2.9.0.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\core\jackson-core\2.9.4\jackson-core-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jdk8\2.9.4\jackson-datatype-jdk8-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\datatype\jackson-datatype-jsr310\2.9.4\jackson-datatype-jsr310-2.9.4.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\jackson\module\jackson-module-parameter-names\2.9.4\jackson-module-parameter-names-2.9.4.jar;C:\Users\haitaoc\.m2\repository\org\springframework\boot\spring-boot-starter-tomcat\2.0.0.RELEASE\spring-boot-starter-tomcat-2.0.0.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\apache\tomcat\embed\tomcat-embed-core\8.5.28\tomcat-embed-core-8.5.28.jar;C:\Users\haitaoc\.m2\repository\org\apache\tomcat\embed\tomcat-embed-el\8.5.28\tomcat-embed-el-8.5.28.jar;C:\Users\haitaoc\.m2\repository\org\apache\tomcat\embed\tomcat-embed-websocket\8.5.28\tomcat-embed-websocket-8.5.28.jar;C:\Users\haitaoc\.m2\repository\org\hibernate\validator\hibernate-validator\6.0.7.Final\hibernate-validator-6.0.7.Final.jar;C:\Users\haitaoc\.m2\repository\javax\validation\validation-api\2.0.1.Final\validation-api-2.0.1.Final.jar;C:\Users\haitaoc\.m2\repository\org\jboss\logging\jboss-logging\3.3.0.Final\jboss-logging-3.3.0.Final.jar;C:\Users\haitaoc\.m2\repository\com\fasterxml\classmate\1.3.1\classmate-1.3.1.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-web\5.0.4.RELEASE\spring-web-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-beans\5.0.4.RELEASE\spring-beans-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-webmvc\5.0.4.RELEASE\spring-webmvc-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-aop\5.0.4.RELEASE\spring-aop-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-context\5.0.4.RELEASE\spring-context-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\springframework\spring-expression\5.0.4.RELEASE\spring-expression-5.0.4.RELEASE.jar;C:\Users\haitaoc\.m2\repository\org\projectlombok\lombok\1.16.16\lombok-1.16.16.jar;C:\Users\haitaoc\.m2\repository\com\google\guava\guava\10.0.1\guava-10.0.1.jar;C:\Users\haitaoc\.m2\repository\com\google\code\findbugs\jsr305\1.3.9\jsr305-1.3.9.jar;C:\Users\haitaoc\.m2\repository\joda-time\joda-time\2.9.9\joda-time-2.9.9.jar io.haitaoc.concurrency.example.aqs.CyclicBarrierExample3
0 is ready
1 is ready
2 is ready
3 is ready
4 is ready
callback is running
0 continue
1 continue
4 continue
3 continue
2 continue
5 is ready
6 is ready
7 is ready
8 is ready
9 is ready
callback is running
9 continue
5 continue
6 continue
7 continue
8 continue

Process finished with exit code 0