Runnable、Callable、Future、FutureTask的区别

转自：https://blog.csdn.net/jdsjlzx/article/details/52912701

FutureTask既是Future、Runnable，又是包装了Callable(如果是Runnable最终也会被转换为Callable )， 它是这两者的合体

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;

public class FutureTest {

    public static class Task implements Runnable {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            System.out.println("run");
        }

    }
    public static class Task2 implements Callable<Integer> {

        @Override
        public Integer call() throws Exception {
            System.out.println("call");
            return fibc(30);
        }

    }

     /**
     * runnable, 无返回值
     */
    public static void testRunnable(){
        ExecutorService executorService = Executors.newCachedThreadPool();

        Future<String> future = (Future<String>) executorService.submit(new Task());
        try {
            System.out.println(future.get());
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        executorService.shutdown();
    }

    /**
     * Callable, 有返回值
     */
    public static void testCallable(){
        ExecutorService executorService = Executors.newCachedThreadPool();

        Future<Integer> future = (Future<Integer>) executorService.submit(new Task2());
        try {
            System.out.println(future.get());
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        executorService.shutdown();
    }

     /**
     * FutureTask则是一个RunnableFuture<V>，即实现了Runnbale又实现了Futrue<V>这两个接口，
     * 另外它还可以包装Runnable(实际上会转换为Callable)和Callable
     * <V>，所以一般来讲是一个符合体了，它可以通过Thread包装来直接执行，也可以提交给ExecuteService来执行
     * ，并且还可以通过v get()返回执行结果，在线程体没有执行完成的时候，主线程一直阻塞等待，执行完则直接返回结果。
     */
    public static void testFutureTask(){
        ExecutorService executorService = Executors.newCachedThreadPool();
        FutureTask<Integer> futureTask = new FutureTask<Integer>(new Task2());

        executorService.submit(futureTask);
        try {
            System.out.println(futureTask.get());
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        executorService.shutdown();
    }

     /**
     * FutureTask则是一个RunnableFuture<V>，即实现了Runnbale又实现了Futrue<V>这两个接口，
     * 另外它还可以包装Runnable(实际上会转换为Callable)和Callable
     * <V>，所以一般来讲是一个符合体了，它可以通过Thread包装来直接执行，也可以提交给ExecuteService来执行
     * ，并且还可以通过v get()返回执行结果，在线程体没有执行完成的时候，主线程一直阻塞等待，执行完则直接返回结果。
     */
    public static void testFutureTask2(){
        ExecutorService executorService = Executors.newCachedThreadPool();
        FutureTask<Integer> futureTask = new FutureTask<Integer>(new Runnable() {

            @Override
            public void run() {
                // TODO Auto-generated method stub
                System.out.println("testFutureTask2 run");
            }
        },fibc(30));

        executorService.submit(futureTask);
        try {
            System.out.println(futureTask.get());
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        executorService.shutdown();
    }

    public static void main(String[] args) {

        testCallable();

    }

    /**
     * 效率低下的斐波那契数列, 耗时的操作
     *
     * @param num
     * @return
     */
    static int fibc(int num) {
        if (num == 0) {
            return 0;
        }
        if (num == 1) {
            return 1;
        }
        return fibc(num - 1) + fibc(num - 2);
    }  

}