从 Java 中的多个线程更改原子值

你好。请帮我解决以下问题：

使用 LongAccumulator 类计算最大和最小累加器。

假设应该有几个线程，生成元素的类型是任意的。这是我的代码：

import java.util.Random;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.LongAccumulator;

public class Main {
    public static LongAccumulator maxValue = new LongAccumulator(Math::max, Integer.MIN_VALUE);
    public static LongAccumulator minValue = new LongAccumulator(Math::min, Integer.MAX_VALUE);

    public static void main(String[] args){
        Random random = new Random();
//        Executor executor = Executors.newCachedThreadPool();
        Executor executor = Executors.newFixedThreadPool(1);
        for (int i = 1; i <= 1000; i++) {
            int taskId = i;
            Runnable task = () -> {
                for (int k = 1; k <= 100_000; k++){
                    int value = random.nextInt(1_000_000);
                    maxValue.accumulate(value);
                    minValue.accumulate(value);
                }
                System.out.println(taskId + ": min " + minValue.get() + ": max " + maxValue.get());
            };
            executor.execute(task);
        }
    }
}

一切正常，但并不像我预期的那样。如果所有任务都放在一个线程中（见第 1 行Executor executor = Executors.newFixedThreadPool(1);），那么一切都会或多或少地完成。如果我们代替这一行Executor executor = Executors.newCachedThreadPool();，或放置多个线程：Executor executor = Executors.newFixedThreadPool(5);，那么代码运行时间会长几倍。实际上，问题在于为什么会出现这种情况，以及如何做到将任务划分为线程不会增加程序运行时间，而是会减少程序运行时间。

更新。按照评论中给出的建议，我将代码更改如下，程序开始在多线程模式下运行得更快：

import java.util.Random;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.LongAccumulator;

public class Main {
    public static LongAccumulator maxValue = new LongAccumulator(Math::max, Integer.MIN_VALUE);
    public static LongAccumulator minValue = new LongAccumulator(Math::min, Integer.MAX_VALUE);

    public static void main(String[] args){
        Executor executor = Executors.newCachedThreadPool();
        Runnable task; // вынес объявление из цикла ниже
        for (int i = 1; i <= 1000; i++) {
            Random random = new Random();  // для каждой задачи создаётся свой Random
            int taskId = i;
            task = () -> {
                for (int k = 1; k <= 100_000; k++){
                    int value = random.nextInt(1_000_000);
                    maxValue.accumulate(value);
                    minValue.accumulate(value);
                }
                System.out.println(taskId + ": min " + minValue.get() + ": max " + maxValue.get());
            };
            executor.execute(task);
        }
    }
}