CachedThreadPool

/**

• CachedThreadPool

• 可缓存的线程

• 当有个请求进入线程池内, 线程池将会启用一个线程

• 当再次有个请求进入线程池内, 并且上个线程未结束, 仍然会启用一个线程

• 当有线程执行完毕后,这个线程不会被清除, 而是被缓存,当有请求进入时, 直接使用缓存线程调用

• 跟 fixedThreadPool 类似, 只不过没有上限(最多Integer最大值), 是一种弹性操作

• 当线程一直不被使用, 缓存最多持续1分钟(AliveTime默认值),就会被线程池销毁

• 内部是 DelayedWorkQueue
  */
  public class T08_CachedThreadPool {

  public static void main(String[] args) {
  ExecutorService service = Executors.newCachedThreadPool();
  // pool size 为0
  System.out.println(service); // java.util.concurrent.ThreadPoolExecutor@7f31245a[Running, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 0]cu'

   for (int i = 0; i < 2; i++) {
       service.execute(() -> {
           try {
               TimeUnit.MILLISECONDS.sleep(500);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }
           System.out.println(Thread.currentThread().getName());
       });
   }
   // pool size 变为2 
   System.out.println(service); // java.util.concurrent.ThreadPoolExecutor@7f31245a[Running, pool size = 2, active threads = 2, queued tasks = 0, completed tasks = 0]
  
  
   try {
       TimeUnit.SECONDS.sleep(80); // 最多持续1分钟,这里sleep80s
   } catch (InterruptedException e) {
       e.printStackTrace();
   }
  
   // pool size 变为0
   System.out.println(service); // java.util.concurrent.ThreadPoolExecutor@7f31245a[Running, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 2]
  

  }
  }