/**
* 7大参数
*
* 特别注意：线程池不允许使用Executors创建、而是通过ThreadPoolExecutor的方式
* 因为FixedThreadPool和SingleThreadExecutor允许请求的的队列长度是Integer.MAX_VALUE、会堆积大量请求、导致OOM
* 因为CachedThreadPool和ScheduledThreadPool允许创建线程数量是Integer.MAX_VALUE、会创建大量线程、导致OOM
*
* ?源码分析1
* ?????????public static ExecutorService newSingleThreadExecutor() {
* ????????????return new Executors.FinalizableDelegatedExecutorService
* ????????????????????(new ThreadPoolExecutor(1, 1,
* ????????????????????????????0L, TimeUnit.MILLISECONDS,
* ????????????????????????????new LinkedBlockingQueue<Runnable>()));
* ????????}
*
* ?源码分析2
* ???????public static ExecutorService newFixedThreadPool(int nThreads) {
* ????????????return new ThreadPoolExecutor(nThreads, nThreads,
* ????????????????????0L, TimeUnit.MILLISECONDS,
* ????????????????????new LinkedBlockingQueue<Runnable>());
* ????????}
*
* ?源码分析3
* ????????public static ExecutorService newCachedThreadPool() {
* ????????????return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
* ????????????????????60L, TimeUnit.SECONDS,
* ????????????????????new SynchronousQueue<Runnable>());
* ????????}
*
*
*
*/
public class Thread10 {
// ?重点：本质：ThreadPoolExecutor7大参数
//public ThreadPoolExecutor(int corePoolSize, ????核心线程池大小
// ?????????????????????????int maximumPoolSize, ?最大核心线程池大小
// ?????????????????????????long keepAliveTime, ??超时了没有人调用就会释放
// ?????????????????????????TimeUnit unit, ???????超时单位
// ?????????????????????????BlockingQueue<Runnable> workQueue, ??阻塞队列
// ?????????????????????????ThreadFactory threadFactory, ????????线程工厂
// ?????????????????????????RejectedExecutionHandler handler) ???拒绝策略
// 重点：本质：4种拒绝策略
// ThreadPoolExecutor.AbortPolicy 银行满了、还有人进来、不处理这个人的、抛出异常
// ThreadPoolExecutor.CallerRunsPolicy 哪来的去哪里
// ThreadPoolExecutor.DiscardPolicy 队列满了、丢掉任务、不会抛出异常
// ThreadPoolExecutor.DiscardOldestPolicy} 队列满了、尝试去和最早的竞争、不会抛出异常
// 读源码的好处、掌握原理、更深入透彻的使用、例如HashMap
// ???????Map map = new HashMap();// 16、0.75
// ???????Map map2 = new HashMap<>(10, 0.5F);
}