目录介绍

• 01.如何捕获run方法异常
• 02.sleep方法为何需要捕获异常
• 03.sleep(0)作用是什么

02.sleep方法为何需要捕获异常

• 先来看一下下面代码

  try {
      Thread.sleep(2000);
  } catch (InterruptedException e) {
      e.printStackTrace();
  }

  
  
• 然后看一下源码
  • 从这里可以看出，当millis为0的时候，并且线程调用了interrupted方法，如果使用sleep则会抛出异常InterruptedException，所以需要捕获一下。
  • sleep方法添加了锁

  public static void sleep(long millis) throws InterruptedException {
      Thread.sleep(millis, 0);
  }
  
  public static void sleep(long millis, int nanos) throws InterruptedException {
      if (millis < 0) {
          throw new IllegalArgumentException("millis < 0: " + millis);
      }
      if (nanos < 0) {
          throw new IllegalArgumentException("nanos < 0: " + nanos);
      }
      if (nanos > 999999) {
          throw new IllegalArgumentException("nanos > 999999: " + nanos);
      }
  
      // The JLS 3rd edition, section 17.9 says: "...sleep for zero
      // time...need not have observable effects."
      if (millis == 0 && nanos == 0) {
          // ...but we still have to handle being interrupted.
          if (Thread.interrupted()) {
            throw new InterruptedException();
          }
          return;
      }
  
      long start = System.nanoTime();
      long duration = (millis * NANOS_PER_MILLI) + nanos;
  
      Object lock = currentThread().lock;
  
      // Wait may return early, so loop until sleep duration passes.
      synchronized (lock) {
          while (true) {
              sleep(lock, millis, nanos);
  
              long now = System.nanoTime();
              long elapsed = now - start;
  
              if (elapsed >= duration) {
                  break;
              }
  
              duration -= elapsed;
              start = now;
              millis = duration / NANOS_PER_MILLI;
              nanos = (int) (duration % NANOS_PER_MILLI);
          }
      }
  }

  
  

03.sleep(0)作用是什么

• Thread.Sleep(0) 。既然是 Sleep 0 毫秒，那么他跟去掉这句代码相比，有啥区别么？
  • 答案是：有，而且区别很明显。Thread.Sleep(0)的作用，就是“触发操作系统立刻重新进行一次CPU竞争”。竞争的结果也许是当前线程仍然获得CPU控制权，也许会换成别的线程获得CPU控制权。这也是我们在大循环里面经常会写一句Thread.Sleep(0)，因为这样就给了其他线程比如Paint线程获得CPU控制权的权力，这样界面就不会假死在那里。
• sleep(0)会抛出异常吗？
  • 会抛出异常，代码如下所示

  public static void sleep(long millis, int nanos)
      throws InterruptedException {
          if (millis < 0) {
              throw new IllegalArgumentException("millis < 0: " + millis);
          }
          if (nanos < 0) {
              throw new IllegalArgumentException("nanos < 0: " + nanos);
          }
          if (nanos > 999999) {
              throw new IllegalArgumentException("nanos > 999999: " + nanos);
          }
  
          // The JLS 3rd edition, section 17.9 says: "...sleep for zero
          // time...need not have observable effects."
          if (millis == 0 && nanos == 0) {
              // ...but we still have to handle being interrupted.
              if (Thread.interrupted()) {
                throw new InterruptedException();
              }
              return;
          }

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