Java 中对象List 转map实践

Gemini19952024-07-25 20:00

java 复制代码

class MyObject {
    Long id;
    String name;

    // Constructor
    public MyObject(Long id, String name) {
        this.id = id;
        this.name = name;
    }

    // Getters
    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }
}

第一种 List 转 Map<Long, String>

java 复制代码

List<MyObject> myObjectList=new ArrayList<>();
//  自行赋值

 Map<Long, String> map = myObjectList.stream()
 					.collect(Collectors.toMap(
                            MyObject::getId,   // key mapper
                            MyObject::getName// value mapper
                    ));

第二种 List 转 Map<Long, List>

java 复制代码

List<MyObject> myObjectList=new ArrayList<>();
//  自行赋值

 Map<Long, List<String>>  map = myObjectList.stream()
                        .collect(Collectors.groupingBy(
                                MyObject::getId, // key mapper
                                Collectors.mapping(MyObject::getName, Collectors.toList()) // value mapper
                        ));