如何在Java8中通过流对Map对象进行按时间段求和？

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Collectors;

public class MapSumByTime {

    public static void main(String[] args) {
        // 创建一个包含时间和数值的示例Map对象
        Map<LocalDateTime, Integer> map = new HashMap<>();
        map.put(LocalDateTime.of(2022, 1, 1, 10, 0), 100);
        map.put(LocalDateTime.of(2022, 1, 1, 11, 0), 200);
        map.put(LocalDateTime.of(2022, 1, 1, 12, 0), 300);
        map.put(LocalDateTime.of(2022, 1, 2, 10, 0), 400);
        map.put(LocalDateTime.of(2022, 1, 2, 11, 0), 500);
        map.put(LocalDateTime.of(2022, 1, 2, 12, 0), 600);

        // 按照时间段进行求和
        Map<LocalDateTime, Integer> sumByTime = map.entrySet().stream()
                .collect(Collectors.groupingBy(entry -> entry.getKey().truncatedTo(ChronoUnit.HOURS),
                        Collectors.summingInt(Map.Entry::getValue)));

        // 输出结果
        sumByTime.forEach((time, sum) -> System.out.println("时间：" + time + " 求和：" + sum));
    }
}