使用streams将Map<String、Map<String、Integer>>转换为Map<String、Integer>

import java.util.HashMap;
import java.util.Map;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        Map<String, Map<String, Integer>> inputMap = new HashMap<>();
        // 添加示例数据
        Map<String, Integer> innerMap1 = new HashMap<>();
        innerMap1.put("A", 1);
        innerMap1.put("B", 2);
        inputMap.put("Key1", innerMap1);

        Map<String, Integer> innerMap2 = new HashMap<>();
        innerMap2.put("C", 3);
        innerMap2.put("D", 4);
        inputMap.put("Key2", innerMap2);

        // 使用streams将Map<String, Map<String, Integer>>转换为Map<String, Integer>
        Map<String, Integer> outputMap = inputMap.entrySet().stream()
                .collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue().values().stream()
                        .reduce(0, Integer::sum)));

        // 打印转换后的结果
        outputMap.forEach((key, value) -> System.out.println(key + ": " + value));
    }
}

Key1: 3
Key2: 7