本文共 3188 字,大约阅读时间需要 10 分钟。
1、利用StringBuilder来拼接5000个单个字符,预计拼接后的长度为5000,如果不是5000,则不是线程安全的。
@Slf4jpublic class StringExample1 { // 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 StringBuilder stringBuilder = new StringBuilder(); public static void main(String[] args) throws InterruptedException { 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(); update(); semaphore.release(); } catch (InterruptedException e) { e.printStackTrace(); } countDownLatch.countDown(); }); } countDownLatch.await(); executorService.shutdown(); log.info("size:{}", stringBuilder.length()); } public static void update() { stringBuilder.append("i"); }}
@Slf4jpublic class StringExample2 { // 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 StringBuffer stringBuffer = new StringBuffer(); public static void main(String[] args) throws InterruptedException { 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(); update(); semaphore.release(); } catch (InterruptedException e) { e.printStackTrace(); } countDownLatch.countDown(); }); } countDownLatch.await(); executorService.shutdown(); log.info("size:{}", stringBuffer.length()); } public static void update() { stringBuffer.append("i"); }}
@Overridepublic synchronized StringBuffer append(String str) { toStringCache = null; super.append(str); return this;}
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