Executors 6种线程池创建

1.newFixedThreadPool：创建一个固定大小的线程池

		ExecutorService threadPool= Executors.newFixedThreadPool(5);
        //2.使用线程池执行任务一
        for (int i=0;i<5;i++){
            //给线程池添加任务
            threadPool.submit(new Runnable() {
                @Override
                public void run() {
                    System.out.println("线程名"+Thread.currentThread().getName()+"在执行任务1");
                }
            });
        }

2.newSingleThreadExecutor:创建单个线程的线程池

        ExecutorService service= Executors.newSingleThreadExecutor();
        for (int i=0;i<5;i++){
            int finalI = i;
            service.submit(()->{
                System.out.println(finalI +"线程名"+Thread.currentThread().getName());//CPU只创建了1个线程，名称始终一样
            });
        }

3.newSingleThreadScheduledExecutor：创建执行定时任务的单个线程的线程池

		ScheduledExecutorService service= Executors.newSingleThreadScheduledExecutor();
        System.out.println("添加任务："+ LocalDateTime.now());
        service.schedule(new Runnable() {
            @Override
            public void run() {
                System.out.println("执行任务："+LocalDateTime.now());
            }
        },3,TimeUnit.SECONDS);//推迟3秒执行任务

4.newScheduledThreadPool：创建执行定时任务的线程池

		ScheduledExecutorService service = Executors.newScheduledThreadPool(5);//5个线程
        System.out.println("添加任务：" + LocalDateTime.now());
        //单独方法
        once(service);
        
 public static void once(ScheduledExecutorService service) {
 		//service里有多个方法具体不详细阐述，看源码
        service.schedule(new Runnable() {
            @Override
            public void run() {
                System.out.println("执行任务:" + LocalDateTime.now());
            }
        }, 3, TimeUnit.SECONDS);//推迟3秒执行
    }

5.newCachedThreadPool：带缓存的线程池，适用于短时间有大量任务的场景，但有可能会占用更多的资源；线程数量随任务量而定。

        ExecutorService service= Executors.newCachedThreadPool();
        //有50个任务
        for(int i=0;i<50;i++){
            int finalI = i;
            service.submit(()->{
                System.out.println(finalI +"线程名"+Thread.currentThread().getName());//线程名有多少个，CPU就创建了多少个线程
            });
        }

6.newWorkStealingPool：创建一个抢占式执行的线程池（任务执行顺序不确定），注意此方法只有在 JDK 1.8+ 版本中才能使用

        ExecutorService executorService = Executors.newWorkStealingPool();
        for (int i = 0; i < 50; i++) {
            int finals = i;
            executorService.submit(()->{
                System.out.println(finals + "线程名" + Thread.currentThread().getName());
            });
        }