线程池

java创建线程池有两种方法

Executors，ThreadPoolExecutor

不建议Executors去创建，而是通过ThreadPoolExecutor。

Executors各个方法的弊端：
   1）newFixedThreadPool和newSingleThreadExecutor:
     主要问题是堆积的请求处理队列可能会耗费非常大的内存，甚至OOM。
   2）newCachedThreadPool和newScheduledThreadPool:
     主要问题是线程数最大数是Integer.MAX_VALUE，可能会创建数量非常多的线程，甚至OOM。

定时调度器：
    //org.apache.commons.lang3.concurrent.BasicThreadFactory
    ScheduledExecutorService executorService = new ScheduledThreadPoolExecutor(1,new BasicThreadFactory.Builder().namingPattern("example-schedule-pool-%d").daemon(true).build());   
　　
　　// com.google.common.util.concurrent.ThreadFactoryBuilder;
　　ThreadFactory build = new ThreadFactoryBuilder().build();
　　ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(8, build);

线程池：
    ThreadFactory namedThreadFactory = new ThreadFactoryBuilder().setNameFormat("demo-pool-%d").build();
    //Common Thread Pool
    ExecutorService pool = new ThreadPoolExecutor(5, 200,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue<Runnable>(1024), namedThreadFactory, new ThreadPoolExecutor.AbortPolicy());

    pool.execute(()-> System.out.println(Thread.currentThread().getName()));
    pool.shutdown();