本篇博客我们主要讲述J.U.C包下的atomic包，在上篇博客“并发模拟”的最后，我们模拟高并发的情形时出现了线程安全问题，怎么解决呢？其实解决的办法有很多中，如直接在add（）方法上加synchronized关键字，还有一种就是用atomic包下的类来解决这个问题，这也是现在比较推荐的一种写法，下面我们给出完整代码：
@Slf4j public class CountExample2 { //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 AtomicInteger count = new AtomicInteger(0); private static void add() { count.incrementAndGet(); // count.getAndIncrement(); } public static void main(String[] args)throws Exception { //定义线程池 ExecutorService executorService = Executors.newCachedThreadPool(); //定义信号量 final Semaphore semaphore = new Semaphore(threadTotal); //定义计数器闭锁 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.get()); } }