Java线程池相关类-Executor框架

Posted 2020-10-14 安卓笔记侠

1.Executor

接口源码：

public interface Executor {

    /**
     * Executes the given command at some time in the future.  The command
     * may execute in a new thread, in a pooled thread, or in the calling
     * thread, at the discretion of the <tt>Executor</tt> implementation.
     *
     * @param command the runnable task
     * @throws RejectedExecutionException if this task cannot be
     * accepted for execution.
     * @throws NullPointerException if command is null
     */
    void execute(Runnable command);
}

接口使用：

public class T01_MyExecutor implements Executor {

    public static void main(String[] args) {
        new T01_MyExecutor().execute(()->System.out.println("hello executor"));
    }

    @Override
    public void execute(Runnable command) {
        //new Thread(command).run();
        command.run();
    }

}

2.ExecutorService

源码：

认识submit方法，扩展了execute方法，具有一个返回值

<T> Future<T> submit(Callable<T> task);

<T> Future<T> submit(Runnable task, T result);

Future<?> submit(Runnable task);

使用：

ExecutorService提供了管理Eecutor生命周期的方法，ExecutorService的生命周期包括了：运行  关闭和终止三种状态。

 

ExecutorService在初始化创建时处于运行状态。

shutdown方法等待提交的任务执行完成并不再接受新任务，在完成全部提交的任务后关闭

shutdownNow方法将强制终止所有运行中的任务并不再允许提交新任务

 

可以将一个Runnable或Callable提交给ExecutorService的submit方法执行，最终返回一上Futire用来获得任务的执行结果或取消任务

（任务执行完成后并返回执行结果）

public class CallableAndFuture {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        Future<String> future = executor.submit(new Callable<String>() {   //接受一上callable实例
            public String call() throws Exception {
                return "MOBIN";
            }
        });
        System.out.println("任务的执行结果："+future.get());
    }
}

输出：

任务的执行结果：MOBIN

3.Executors

提供了一系列静态工厂方法用于创建各种线程池

   newFixedThreadPool:创建可重用且固定线程数的线程池，如果线程池中的所有线程都处于活动状态，此时再提交任务就在队列中等待，直到有可用线程；如果线程池中的某个线程由于异常而结束时，线程池就会再补充一条新线程。

ScheduledExecutorService executor = Executors.newScheduledThreadPool(5);

4.ThreadPool

线程池的概念

public static void main(String[] args) throws InterruptedException {
        ExecutorService service = Executors.newFixedThreadPool(5); //execute submit
        for (int i = 0; i < 6; i++) {
            service.execute(() -> {
                try {
                    TimeUnit.MILLISECONDS.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName());
            });
        }
        System.out.println(service);
        
        service.shutdown();
        System.out.println(service.isTerminated());
        System.out.println(service.isShutdown());
        System.out.println(service);
        
        TimeUnit.SECONDS.sleep(5);
        System.out.println(service.isTerminated());
        System.out.println(service.isShutdown());
        System.out.println(service);
    }

5.Future

public static void main(String[] args) throws InterruptedException, ExecutionException {
        
        FutureTask<Integer> task = new FutureTask<>(()->{
            TimeUnit.MILLISECONDS.sleep(500);
            return 1000;
        }); //new Callable () { Integer call();}
        
        new Thread(task).start();
        
        System.out.println(task.get()); //阻塞
        
        //*******************************
        ExecutorService service = Executors.newFixedThreadPool(5);
        Future<Integer> f = service.submit(()->{
            TimeUnit.MILLISECONDS.sleep(500);
            return 1;
        });
        System.out.println(f.get());
        System.out.println(f.isDone());
        
    }

6.