Java多线程教程之如何利用Future实现携带结果的任务

@FunctionalInterface
public interface Runnable {
    public abstract void run();
}

多线程future

public interface Future<V> {
 
    // 取消任务
    boolean cancel(boolean mayInterruptIfRunning);
 
    // 判断是否已经取消
    boolean isCancelled();
    
    // 如果任务已经结束返回 true
    boolean isDone();
    
    // 若有必要会一直阻塞直到结束并返回结果
    V get() throws InterruptedException, ExecutionException;
 
    // 若有必要会阻塞指定的时间等待结束并返回结果
    V get(long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException;
}

public class FutureTask<V> implements RunnableFuture<V> {
    ......
}

public interface RunnableFuture<V> extends Runnable, Future<V> {
    void run();
}

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
 
/**
 * @author ：jhys
 * @date ：Created in 2021/7/6 14:43
 * @Description ：
 */
public class FutureTest1 {
    public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        System.out.println(LocalDateTime.now() + ": thread start");
        Future<Integer> future = executor.submit(() -> {
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(LocalDateTime.now() + ": task start");
            int sum = 0;
            for (int i = 0; i <= 10; i++) {
                sum += i;
            }
            return sum;
        });
        executor.shutdown();
        try {
            Integer ret = future.get();
            System.out.println(LocalDateTime.now() + ": ret = " + ret);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("finish");
    }
}

public class FutureTest {
 
    public static void main(String[] args) {
 
        FutureTask<Integer> future = new FutureTask<>(() -> {
            Thread.sleep(3000);
            System.out.println(LocalDateTime.now() + ": task start");
 
            int sum = 0;
            for (int i =0; i <= 10; i++) {
                sum += i;
            }
            return sum;
        });
 
        ExecutorService executor = Executors.newSingleThreadExecutor();
        // 注意这里的区别，不需要显示获取返回值
        executor.submit(future);
        executor.shutdown();
 
        try {
            System.out.println(LocalDateTime.now() + ": ret = " + future.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        System.out.println("finish");
    }
 
}