并发编程与高并发解决方案学习(J.U.C之AQS-CountDownLatch、Semaphore)_c高并发解决方案-程序员宅基地

※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int类型表示状态 state=0表示还没有线程获取锁 state=1表示有现成获取锁，大于1表示可重入锁数量

※使用方法是继承 AQS使用模板方法模式，继承模板方法，复写其中的方法

※子类通过继承并通过实现它的方法管理其状态{acquire和release}的方法操作状态

※可以同时实现排它锁和共享锁模式(
独占、共享)

AQS同步组件（
CountDownLatch、Semaphore、CyclicBarrier、ReentrantLock、Condition、FutureTask）

CountDownLatch(作用类似于join())
 同步辅助类，可以实现阻塞的作用，同一时间只能有一个线程操作该计数器，调用该类的await类会一直处于阻塞状态，直到其他线程调用countDown方法，使当前计数器的值为0（计数器不可以重置）

使用场景：程序执行需要等待某个条件完成之后才能继续执行后续的操作，典型应用例如：并行计算（ 当某个处理的运算量很大的时候，可以将该运算任务拆分为多个子任务，等待所有子任务都执行完之后，父任务再拿到所有子任务运行结果进行汇总）。

import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

@Slf4j
public class CountDownLatchExample1 {
    private final static int threadCount = 20;
    public static void main(String[] args) throws Exception {
        ExecutorService exec = Executors.newCachedThreadPool();
        final CountDownLatch countDownLatch = new CountDownLatch(threadCount);
        for (int i = 0; i < threadCount; i++) {
            final int threadNum = i;
            exec.execute(() -> {
                try {
                    test(threadNum);
                } catch (Exception e) {
                    log.error("exception", e);
                } finally {
                    countDownLatch.countDown();
                }
            });
        }
        countDownLatch.await();
        log.info("finish");
        exec.shutdown();
    }

    private static  void test(int threadNum) throws Exception {
        Thread.sleep(100);
        log.info("{}", threadNum);
        Thread.sleep(100);
    }
}

输出结果

15:54:06.904 [pool-1-thread-1] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 0
15:54:06.904 [pool-1-thread-8] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 7
15:54:06.905 [pool-1-thread-19] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 18
15:54:06.904 [pool-1-thread-6] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 5
15:54:06.904 [pool-1-thread-7] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 6
15:54:06.904 [pool-1-thread-4] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 3
15:54:06.904 [pool-1-thread-5] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 4
15:54:06.904 [pool-1-thread-3] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 2
15:54:06.904 [pool-1-thread-2] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 1
15:54:06.904 [pool-1-thread-9] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 8
15:54:06.905 [pool-1-thread-18] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 17
15:54:06.904 [pool-1-thread-10] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 9
15:54:06.905 [pool-1-thread-17] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 16
15:54:06.904 [pool-1-thread-11] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 10
15:54:06.905 [pool-1-thread-20] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 19
15:54:06.905 [pool-1-thread-16] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 15
15:54:06.905 [pool-1-thread-13] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 12
15:54:06.904 [pool-1-thread-12] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 11
15:54:06.905 [pool-1-thread-15] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 14
15:54:06.905 [pool-1-thread-14] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - 13
15:54:07.009 [main] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample1 - finish

案例2（起了很多线程去完成任务，但是这个任务指向给指定的时间，操作这个时间没做完，也不管了）

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;

@Slf4j
public class CountDownLatchExample2 {
    private final static int threadCount = 200;
    public static void main(String[] args) throws Exception {
        ExecutorService exec = Executors.newCachedThreadPool();
        final CountDownLatch countDownLatch = new CountDownLatch(threadCount);
        for (int i = 0; i < threadCount; i++) {
            final int threadNum = i;
            exec.execute(() -> {
                try {
                    test(threadNum);
                } catch (Exception e) {
                    log.error("exception", e);
                } finally {
                    countDownLatch.countDown();
                }
            });
        }
        countDownLatch.await(10, TimeUnit.MILLISECONDS);
        log.info("finish");
        exec.shutdown();
    }

    private static void test(int threadNum) throws Exception {
        Thread.sleep(1000);
        log.info("{}", threadNum);
    }
}

输出结果

15:57:13.433 [main] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - finish
15:57:14.423 [pool-1-thread-1] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 0
15:57:14.435 [pool-1-thread-4] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 3
15:57:14.436 [pool-1-thread-3] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 2
15:57:14.436 [pool-1-thread-2] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 1
15:57:14.438 [pool-1-thread-5] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 4
15:57:14.441 [pool-1-thread-8] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 7
15:57:14.442 [pool-1-thread-7] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 6
15:57:14.442 [pool-1-thread-6] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 5
15:57:14.442 [pool-1-thread-11] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 10
15:57:14.443 [pool-1-thread-10] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 9
15:57:14.443 [pool-1-thread-9] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 8
15:57:14.443 [pool-1-thread-13] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 12
15:57:14.443 [pool-1-thread-12] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 11
15:57:14.443 [pool-1-thread-15] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 14
15:57:14.444 [pool-1-thread-14] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 13
15:57:14.444 [pool-1-thread-20] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 19
15:57:14.444 [pool-1-thread-19] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 18
15:57:14.447 [pool-1-thread-18] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 17
15:57:14.447 [pool-1-thread-16] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 15
15:57:14.447 [pool-1-thread-17] INFO com.mmall.concurrency.example.aqs.CountDownLatchExample2 - 16

调用shutdown并不是第一时间将线程都全部销毁掉，而是让当前已有的线程全部执行完，之后再把这个线程池销毁掉。

Semaphore 信号量(控制并发访问的线程个数，类似于有限的链表，常用语仅能提供有限个访问的资源,比如 控制数据库连接数)

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;

@Slf4j
public class SemaphoreExample1 {
    private final static int threadCount = 20;
    public static void main(String[] args) throws Exception {
        ExecutorService exec = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(3);
        for (int i = 0; i < threadCount; i++) {
            final int threadNum = i;
            exec.execute(() -> {
                try {
                    semaphore.acquire(); // 每次获取一个许可
                    test(threadNum);
                    semaphore.release(); // 每次释放一个许可
                } catch (Exception e) {
                    log.error("exception", e);
                }
            });
        }
        exec.shutdown();
    }

    private static void test(int threadNum) throws Exception {
        log.info("{}", threadNum);
        Thread.sleep(1000);
    }
}

输出结果(一次3条输出)

15:59:19.291 [pool-1-thread-2] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 1
15:59:19.291 [pool-1-thread-1] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 0
15:59:19.291 [pool-1-thread-3] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 2
15:59:20.309 [pool-1-thread-4] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 3
15:59:20.310 [pool-1-thread-5] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 4
15:59:20.310 [pool-1-thread-6] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 5
15:59:21.310 [pool-1-thread-7] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 6
15:59:21.310 [pool-1-thread-8] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 7
15:59:21.311 [pool-1-thread-9] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 8
15:59:22.310 [pool-1-thread-10] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 9
15:59:22.310 [pool-1-thread-11] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 10
15:59:22.311 [pool-1-thread-12] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 11
15:59:23.311 [pool-1-thread-13] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 12
15:59:23.311 [pool-1-thread-14] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 13
15:59:23.312 [pool-1-thread-15] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 14
15:59:24.311 [pool-1-thread-16] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 15
15:59:24.311 [pool-1-thread-17] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 16
15:59:24.312 [pool-1-thread-18] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 17
15:59:25.312 [pool-1-thread-20] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 19
15:59:25.312 [pool-1-thread-19] INFO com.mmall.concurrency.example.aqs.SemaphoreExample1 - 18

import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

@Slf4j
public class SemaphoreExample2 {
    private final static int threadCount = 20;
    public static void main(String[] args) throws Exception {
        ExecutorService exec = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(3);
        for (int i = 0; i < threadCount; i++) {
            final int threadNum = i;
            exec.execute(() -> {
                try {
                    semaphore.acquire(3); // 每次获取多个许可
                    test(threadNum);
                    semaphore.release(3); // 每次释放多个许可
                } catch (Exception e) {
                    log.error("exception", e);
                }
            });
        }
        exec.shutdown();
    }

    private static void test(int threadNum) throws Exception {
        log.info("{}", threadNum);
        Thread.sleep(1000);
    }
}

输出结果（一次一条输出）

16:00:37.474 [pool-1-thread-1] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 0
16:00:38.480 [pool-1-thread-2] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 1
16:00:39.480 [pool-1-thread-3] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 2
16:00:40.481 [pool-1-thread-4] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 3
16:00:41.482 [pool-1-thread-5] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 4
16:00:42.482 [pool-1-thread-6] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 5
16:00:43.483 [pool-1-thread-7] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 6
16:00:44.483 [pool-1-thread-8] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 7
16:00:45.484 [pool-1-thread-9] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 8
16:00:46.484 [pool-1-thread-10] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 9
16:00:47.484 [pool-1-thread-11] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 10
16:00:48.485 [pool-1-thread-12] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 11
16:00:49.485 [pool-1-thread-13] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 12
16:00:50.485 [pool-1-thread-14] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 13
16:00:51.486 [pool-1-thread-15] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 14
16:00:52.486 [pool-1-thread-17] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 16
16:00:53.486 [pool-1-thread-16] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 15
16:00:54.486 [pool-1-thread-18] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 17
16:00:55.487 [pool-1-thread-19] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 18
16:00:56.488 [pool-1-thread-20] INFO com.mmall.concurrency.example.aqs.SemaphoreExample2 - 19

案例（假如当前并发数是3，超过3个就丢弃）

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;

@Slf4j
public class SemaphoreExample3 {
    private final static int threadCount = 20;
    public static void main(String[] args) throws Exception {
        ExecutorService exec = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(3);
        for (int i = 0; i < threadCount; i++) {
            final int threadNum = i;
            exec.execute(() -> {
                try {
                    if (semaphore.tryAcquire()) { // 尝试获取一个许可
                        test(threadNum);
                        semaphore.release(); // 释放一个许可
                    }
                } catch (Exception e) {
                    log.error("exception", e);
                }
            });
        }
        exec.shutdown();
    }

    private static void test(int threadNum) throws Exception {
        log.info("{}", threadNum);
        Thread.sleep(1000);
    }
}

输出结果

16:01:45.406 [pool-1-thread-2] INFO com.mmall.concurrency.example.aqs.SemaphoreExample3 - 1
16:01:45.405 [pool-1-thread-1] INFO com.mmall.concurrency.example.aqs.SemaphoreExample3 - 0
16:01:45.413 [pool-1-thread-3] INFO com.mmall.concurrency.example.aqs.SemaphoreExample3 - 2

尝试获得许可，只让执行5秒

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;

@Slf4j
public class SemaphoreExample4 {
    private final static int threadCount = 20;
    public static void main(String[] args) throws Exception {
        ExecutorService exec = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(3);
        for (int i = 0; i < threadCount; i++) {
            final int threadNum = i;
            exec.execute(() -> {
                try {
                    if (semaphore.tryAcquire(5000, TimeUnit.MILLISECONDS)) { // 尝试获取一个许可
                        test(threadNum);
                        semaphore.release(); // 释放一个许可
                    }
                } catch (Exception e) {
                    log.error("exception", e);
                }
            });
        }
        exec.shutdown();
    }

    private static void test(int threadNum) throws Exception {
        log.info("{}", threadNum);
        Thread.sleep(1000);
    }
}

输出结果(一次三条输出)

16:02:31.454 [pool-1-thread-3] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 2
16:02:31.454 [pool-1-thread-1] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 0
16:02:31.454 [pool-1-thread-2] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 1
16:02:32.463 [pool-1-thread-4] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 3
16:02:32.464 [pool-1-thread-5] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 4
16:02:32.464 [pool-1-thread-6] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 5
16:02:33.464 [pool-1-thread-8] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 7
16:02:33.464 [pool-1-thread-7] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 6
16:02:33.465 [pool-1-thread-9] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 8
16:02:34.465 [pool-1-thread-10] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 9
16:02:34.465 [pool-1-thread-11] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 10
16:02:34.466 [pool-1-thread-12] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 11
16:02:35.465 [pool-1-thread-13] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 12
16:02:35.466 [pool-1-thread-14] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 13
16:02:35.466 [pool-1-thread-15] INFO com.mmall.concurrency.example.aqs.SemaphoreExample4 - 14

本文链接：https://blog.csdn.net/Andy2019/article/details/79784000

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文章浏览阅读5.9k次。https://jaywcjlove.github.io/awesome-mac/ 这个仓库主要是收集非常好用的Mac应用程序、软件以及工具，主要面向开发者和设计师。有这个想法是因为我最近发了一篇较为火爆的涨粉儿微信公众号文章《工具武装的前端开发工程师》，于是建了这么一个仓库，持续更新作为补充，搜集更多好用的软件工具。请Star、Pull Request或者使劲搓它 issu_awesomemac

java前端技术---jquery基础详解_简介java中jquery技术-程序员宅基地

文章浏览阅读616次。一.jquery简介 jQuery是一个快速的，简洁的javaScript库，使用户能更方便地处理HTML documents、events、实现动画效果，并且方便地为网站提供AJAX交互 jQuery 的功能概括1、html 的元素选取2、html的元素操作3、html dom遍历和修改4、js特效和动画效果5、css操作6、html事件操作7、ajax_简介java中jquery技术

Ant Design Table换滚动条的样式_ant design ::-webkit-scrollbar-corner-程序员宅基地

文章浏览阅读1.6w次，点赞5次，收藏19次。我修改的是表格的固定列滚动而产生的滚动条引用Table的组件的css文件中加入下面的样式：.ant-table-body{ &amp;::-webkit-scrollbar { height: 5px; } &amp;::-webkit-scrollbar-thumb { border-radius: 5px; -webkit-box..._ant design ::-webkit-scrollbar-corner

javaWeb毕设分享健身俱乐部会员管理系统【源码+论文】-程序员宅基地

文章浏览阅读269次。基于JSP的健身俱乐部会员管理系统项目分享:见文末!

论文开题报告怎么写？_开题报告研究难点-程序员宅基地

文章浏览阅读1.8k次，点赞2次，收藏15次。同学们，是不是又到了一年一度写开题报告的时候呀？是不是还在为不知道论文的开题报告怎么写而苦恼?Take it easy!我带着倾尽我所有开题报告写作经验总结出来的最强保姆级开题报告解说来啦，一定让你脱胎换骨，顺利拿下开题报告这个高塔，你确定还不赶快点赞收藏学起来吗？_开题报告研究难点

原生JS 与 VUE获取父级、子级、兄弟节点的方法及一些DOM对象的获取_获取子节点的路径 vue-程序员宅基地

文章浏览阅读6k次，点赞4次，收藏17次。原生先获取对象var a = document.getElementById("dom");vue先添加ref <div class="" ref="divBox">获取对象let a = this.$refs.divBox获取父、子、兄弟节点方法var b = a.childNodes; 获取a的全部子节点 var c = a.parentNode; 获取a的父节点var d = a.nextSbiling; 获取a的下一个兄弟节点 var e = a.previ_获取子节点的路径 vue