Java-8 Streams:将List<{String，List<String>}>转换为Map<String，List<String>>

import java.util.*;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<Map<String, List<String>>> list = new ArrayList<>();

        // 创建测试数据
        Map<String, List<String>> map1 = new HashMap<>();
        map1.put("key1", Arrays.asList("value1", "value2", "value3"));
        map1.put("key2", Arrays.asList("value4", "value5"));

        Map<String, List<String>> map2 = new HashMap<>();
        map2.put("key3", Arrays.asList("value6", "value7"));
        map2.put("key4", Arrays.asList("value8"));

        list.add(map1);
        list.add(map2);

        // 将List<{String，List<String>}>转换为Map<String，List<String>>
        Map<String, List<String>> result = list.stream()
                .flatMap(map -> map.entrySet().stream())
                .collect(Collectors.toMap(
                        Map.Entry::getKey,
                        Map.Entry::getValue,
                        (oldValue, newValue) -> {
                            List<String> mergedList = new ArrayList<>(oldValue);
                            mergedList.addAll(newValue);
                            return mergedList;
                        }
                ));

        // 打印结果
        for (Map.Entry<String, List<String>> entry : result.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

key1: [value1, value2, value3]
key2: [value4, value5]
key3: [value6, value7]
key4: [value8]