Java中 Map、List 、对象、json互转

标题list

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
 
public class ListMapToNewMapExample {
    public static void main(String[] args) {
        List<Map<String, Object>> listOfMaps = Arrays.asList(
            createMap("id", 1, "name", "Alice", "age", 25),
            createMap("id", 2, "name", "Bob", "age", 30),
            createMap("id", 3, "name", "Charlie", "age", 35)
        );
 
        Map<Integer, Map<String, Object>> newMap = listOfMaps.stream()
            .collect(Collectors.toMap(
                map -> (Integer) map.get("id"), // 取出"id"字段作为新Map的key
                map -> { // 取出"name"和"age"字段，生成新的Map
                    Map<String, Object> result = new HashMap<>();
                    result.put("name", map.get("name"));
                    result.put("age", map.get("age"));
                    return result;
                }
            ));
 
        newMap.forEach((id, data) -> {
            System.out.println("ID: " + id + ", Name: " + data.get("name") + ", Age: " + data.get("age"));
        });
    }
 
    private static Map<String, Object> createMap(Object... keyValues) {
        if (keyValues.length % 2 != 0) {
            throw new IllegalArgumentException("Invalid key/value pairs");
        }
 
        Map<String, Object> map = new HashMap<>();
        for (int i = 0; i < keyValues.length; i += 2) {
            map.put((String) keyValues[i], keyValues[i + 1]);
        }
        return map;
    }
}