FutureTask和CompletableFuture的模拟使用

 模拟了查询耗时操作，并使用FutureTask和CompletableFuture分别获取计算结果，统计执行时长

package org.alllearn.futurtask;

import com.google.common.base.Stopwatch;
import com.google.common.collect.Lists;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.Setter;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.FutureTask;
import java.util.stream.Collectors;

public class CompletableFutureTest {
    public static void main(String[] args) {

        CompletableFutureTest test = new CompletableFutureTest();
        List users = test.getUsers();
        //流计算的简单使用
        Stopwatch started = Stopwatch.createStarted();
        double average = users.stream().mapToInt(User::getAge).average().getAsDouble();
        System.out.println(average + "  " + started.elapsed());

        //模拟通过id集合去其他表批量查询数据
        //单线程任务分割，数据库承受不了大量id的in查询
        List> partition1 = Lists.partition(users, users.size() / 200);
        started.reset();
        started.start();
        double average1 = partition1.stream().mapToDouble(test::select).average().getAsDouble();
        System.out.println(average1 + "  " + started.elapsed());


        //多线程任务两种方案FutureTask、CompletableFuture
        int cpu = Runtime.getRuntime().availableProcessors();
        //计算密集型cpu+1，io密集型cpu*2
        ForkJoinPool forkJoinPool = new ForkJoinPool(cpu + 1);
        List> partition2 = Lists.partition(users, users.size() / 200);


        //FutureTask
        started.reset();
        started.start();
        double average2 = partition2.stream()
                .map(u -> {
                    FutureTask futureTask = new FutureTask<>(() -> test.select(u));
                    forkJoinPool.submit(futureTask);
                    return futureTask;
                })
                .collect(Collectors.toList())
                .stream().
                mapToDouble(f -> {
                    try {
                        return f.get();
                    } catch (InterruptedException | ExecutionException e) {
                        throw new RuntimeException(e);
                    }
                })
                .average()
                .getAsDouble();
        System.out.println(average2 + "  " + started.elapsed());

        //CompletableFuture
        started.reset();
        started.start();
        double average3 = partition2.stream()
                .map(u -> CompletableFuture.supplyAsync(() -> test.select(u), forkJoinPool))
                .collect(Collectors.toList())
                .stream().
                mapToDouble(CompletableFuture::join)
                .average()
                .getAsDouble();
        forkJoinPool.shutdown();
        System.out.println(average3 + "  " + started.elapsed());
    }

    //模拟查询耗时
    public Double select(List user) {
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        return 1D;
        //return Math.random();
    }

    //模拟获取用户
    public List getUsers() {
        List users = new ArrayList<>();
        for (int i = 0; i < 20000; i++) {
            users.add(new User(i, "user" + i, 1));
        }
        return users;
    }

    @Getter
    @Setter
    @AllArgsConstructor
    static class User {
        private int id;
        private String name;
        private int age;
    }

}

运行结果