调用与获取 ForkJoinPool [重复]

Question

前提：我对并发不是很熟悉。

看一下这段代码：

import java.util.List;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.IntStream;

public class TestSync {

    public static void main(String[] args) {
        List<Integer> intArray = IntStream.rangeClosed(1, 500).boxed().toList();

        System.out.println("Element size: " + intArray.size());
        
        AtomicInteger i = new AtomicInteger(intArray.size());
        ForkJoinPool customThreadPool = new ForkJoinPool(50);
        
        customThreadPool.submit( () -> {
            intArray.parallelStream().forEach(sp -> {
                System.out.println("Remaining int: " + i.decrementAndGet());
            });
        }).invoke();
        customThreadPool.shutdown();
    }

}

相关输出为：

Element size: 500
Remaining int: 499
Remaining int: 498
Remaining int: 497
Remaining int: 495
Remaining int: 494
Remaining int: 493
Remaining int: 492
Remaining int: 491
Remaining int: 490
Remaining int: 489
Remaining int: 488
Remaining int: 487
....
Remaining int: -74
Remaining int: -75
Remaining int: -66
Remaining int: -77
Remaining int: -78
Remaining int: -79
Remaining int: -80
Remaining int: -81
Remaining int: -82
Remaining int: -83
...

如果我将

invoke()

替换为

get()

，负数将永远不会出现。

有人可以帮我理解

invoke()

和

get()

之间的区别吗？

Answer 1

当您在 ForkJoinTask 上执行

invoke()

时，您会强制它执行。 但在你已经将它提交到池中执行之前，所以你执行了两次。

执行

get()

将等待任务（已提交到池中）完成并返回结果。