Runnable、Callable、Future、FutureTask的區別

 

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

FutureTask既是Future、Runnable，又是包裝了Callable(如果是Runnable最終也會被轉換為Callable )， 它是這兩者的合體

 

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, 無返回值 
     */  
    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則是一個RunnableFuture<V>，即實現了Runnbale又實現了Futrue<V>這兩個接口， 
     * 另外它還可以包裝Runnable(實際上會轉換為Callable)和Callable 
     * <V>，所以一般來講是一個符合體了，它可以通過Thread包裝來直接執行，也可以提交給ExecuteService來執行 
     * ，並且還可以通過v get()返回執行結果，在線程體沒有執行完成的時候，主線程一直阻塞等待，執行完則直接返回結果。 
     */  
    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則是一個RunnableFuture<V>，即實現了Runnbale又實現了Futrue<V>這兩個接口， 
     * 另外它還可以包裝Runnable(實際上會轉換為Callable)和Callable 
     * <V>，所以一般來講是一個符合體了，它可以通過Thread包裝來直接執行，也可以提交給ExecuteService來執行 
     * ，並且還可以通過v get()返回執行結果，在線程體沒有執行完成的時候，主線程一直阻塞等待，執行完則直接返回結果。 
     */  
    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數列, 耗時的操作 
     *  
     * @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);  
    }  

}