异步回调

Future 设计的初衷：对未来的结果建模

package com.example.juc;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class TestAsync {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        // 无返回值的异步回调
        CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {
            try {
                TimeUnit.SECONDS.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "Thread-> void");
        });

        System.out.println(1111); // 1111
        future.get(); // 等待2s ForkJoinPool.commonPool-worker-9Thread-> void

        // 有返回值的异步回调
        CompletableFuture<Integer> future1 = CompletableFuture.supplyAsync(() -> {
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.println(Thread.currentThread().getName() + "Thread-> Integer");
            int i = 10 / 0;
            return 1;
        });

        System.out.println(future1.whenComplete((u, t) -> {
            System.out.println("u->" + u);
            System.out.println("t->" + t);
        }).exceptionally((e) -> {
            System.out.println(e.getMessage());
            return 2;
        }).get());

    }

}

1111
ForkJoinPool.commonPool-worker-9Thread-> void
ForkJoinPool.commonPool-worker-9Thread-> Integer
u->null
t->java.util.concurrent.CompletionException: java.lang.ArithmeticException: / by zero
java.lang.ArithmeticException: / by zero
2