Java并发编程 - 线程安全性之简介

接下来的几篇分析当中都会以这段问题代码为基础进行讲解……（对于数量 +1 业务：5000个请求，200个并发）

包括接下来有四个注解（标记而已）代表不同含义：

1. @NotRecommend：课程里用来标记【不推荐】的类或者写法
2. @NotThreadSafe：课程里用来标记【线程不安全】的类或者写法
3. @Recommend：课程里用来标记【推荐】的类或者写法
4. @ThreadSafe：课程里用来标记【线程安全】的类或者写法

package com.mmall.concurrency;
 
import com.mmall.concurrency.annoations.NotThreadSafe;
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
@NotThreadSafe
public class ConcurrencyTest {
 
    // 请求总数
    public static int clientTotal = 5000;
 
    // 同时并发执行的线程数
    public static int threadTotal = 200;
 
    public static int count = 0;
 
    public static void main(String[] args) throws Exception {
        ExecutorService executorService = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(threadTotal);
        final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
        for (int i = 0; i < clientTotal; i++) {
            executorService.execute(() -> {
                try {
                    semaphore.acquire();
                    add();
                    semaphore.release();
                } catch (Exception e) {
                    log.error("exception", e);
                }
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        log.info("count:{}", count);
    }
 
    private static void add() {
        count++;
    }
}