Java框架如何处理函数式编程中的并行性和并发性？

import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveTask;

public class ArraySum extends RecursiveTask<Long> {

    private int[] arr;
    private int start;
    private int end;

    public ArraySum(int[] arr, int start, int end) {
        this.arr = arr;
        this.start = start;
        this.end = end;
    }

    @Override
    public Long compute() {
        if (end - start <= 100) {
            return calculateSum(arr, start, end);
        } else {
            int mid = (start + end) / 2;
            ArraySum left = new ArraySum(arr, start, mid);
            ArraySum right = new ArraySum(arr, mid, end);
            return left.fork().join() + right.fork().join();
        }
    }

    private long calculateSum(int[] arr, int start, int end) {
        long sum = 0;
        for (int i = start; i < end; i++) {
            sum += arr[i];
        }
        return sum;
    }

    public static void main(String[] args) {
        int[] arr = new int[100000];
        ForkJoinPool pool = new ForkJoinPool();
        long sum = pool.invoke(new ArraySum(arr, 0, arr.length));
        System.out.println("Sum: " + sum);
    }
}

import java.util.concurrent.ConcurrentHashMap;

public class ConcurrentMap {

    public static void main(String[] args) {
        ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
        for (int i = 0; i < 100000; i++) {
            map.put("key" + i, i);
        }

        for (int i = 0; i < 10; i++) {
            Thread thread = new Thread(() -> {
                for (String key : map.keySet()) {
                    int value = map.get(key);
                    System.out.println("Thread " + Thread.currentThread().getName() + ": " + key + "=" + value);
                }
            });
            thread.start();
        }
    }
}