JuC并发编程-ForkJoin与异步回调

1、ForkJoin

特点：工作窃取 里边维护的是双端队列

package com.zkw.JUC并发编程.forkjoin;

import java.util.concurrent.RecursiveTask;

public class ForkJoinDemon extends RecursiveTask<Long> {
    
    

    private Long start;
    private Long end;

    //临界值
    private Long temp = 1_0000L;

    public ForkJoinDemon(Long start, Long end) {
    
    
        this.start = start;
        this.end = end;
    }

    @Override
    protected Long compute() {
    
    
        if (end-start<temp){
    
    
            Long sum = 0L;
            for (Long i = start; i <= end; i++) {
    
    
                sum+=i;
            }
            return sum;
        } else{
    
    
            Long middle = (end+start)/2;
            ForkJoinDemon task1 = new ForkJoinDemon(start, middle);
            task1.fork(); //拆分任务，把线程压入到队列中
            ForkJoinDemon task2 = new ForkJoinDemon(middle + 1, end);
            task2.fork();

            return task1.join() + task2.join();
        }
    }
}

package com.zkw.JUC并发编程.forkjoin;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.stream.LongStream;

public class Test {
    
    
    public static void main(String[] args) throws ExecutionException, InterruptedException {
    
    
        //test1();//9288
        //test2();//8273
        test3();//238
    }

    public static void test1(){
    
    
        Long sum = 0L;
        long start = System.currentTimeMillis();
        for (Long i = 1L; i <= 10_0000_0000L; i++) {
    
    
            sum+=i;
        }
        long end = System.currentTimeMillis();
        System.out.println("sum = "+sum+" "+"时间："+(end-start));
    }
    // ForkJoin
     public static void test2() throws ExecutionException, InterruptedException {
    
    
        long start = System.currentTimeMillis();

         ForkJoinPool forkJoinPool = new ForkJoinPool();
         ForkJoinDemon task = new ForkJoinDemon(1L, 10_0000_0000L);
         ForkJoinTask<Long> submit = forkJoinPool.submit(task);//提交任务
         Long sum = submit.get();

         long end = System.currentTimeMillis();
        System.out.println("sum = "+sum+" "+"时间："+(end-start));

     }

     //Stream 并行流
     public static void test3(){
    
    
        long start = System.currentTimeMillis();

        Long sum = LongStream.range(0L,10_0000_0001L).parallel().reduce(0,Long::sum);
        long end = System.currentTimeMillis();
        System.out.println("sum = "+sum+" "+"时间："+(end-start));
     }
}

2、异步回调

package com.zkw.JUC并发编程.future;

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

/**
 * 异步回调 CompletableFuture
 * 异步执行
 * 成功回调
 * 失败回调
 */
public class Demon01 {
    
    
    public static void main(String[] args) throws ExecutionException, InterruptedException {
    
    
     /*   //没有返回值的异步回调
        CompletableFuture<Void> future = CompletableFuture.runAsync(()->{
            try {
                TimeUnit.SECONDS.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+"runAsync=>Void");
        });
        System.out.println("1111111");
        future.get();// 获取阻塞执行结果*/

     //有返回值的 supplyAsync 异步回调
     // ajax ，成功和失败回调
        CompletableFuture<Integer> future1 = CompletableFuture.supplyAsync(()->{
    
    
            System.out.println(Thread.currentThread().getName()+"supplyAsync=>Integer");
            int i= 10/0;
            return 1024;
        });
        System.out.println(future1.whenComplete((t, u) -> {
    
    
            System.out.println("t=>" + t);//正常的返回结果
            System.out.println("u=>" + u); //错误信息
        }).exceptionally((e) -> {
    
    
            System.out.println(e.getMessage());
            return 233; //错误的返回结果
        }).get());
    }
}