Collectors.toMap方法简介说明

下文笔者讲述Collectors.toMap方法的功能简介说明,如下所示

Collectors.toMap方法的功能简介

将一个集合转换为一个map对象

注意事项:
    当出现重复key时,会产生java.lang.IllegalStateException异常

例:定义实体类

@Data
public class User {

    private Integer id;         
    private Integer age;    
    private String name;   
    private String address;    
}

例:Collectors.toMap方法示例

/**
 * @description: list 转 Map 操作
 */
public class ListToMap {
    public static void main(String[] args) {
        User User = new User(1,1,"Java265-1","测试1");
        User User1 = new User(2,2,"Java265-2","测试2");
        User User2 = new User(3,3,"Java265-3","测试3");
        ArrayList<User> Users = new ArrayList<>();
        Users.add(User);
        Users.add(User1);
        Users.add(User2); 

        Map<String, String> mapUser = Users.stream().collect(Collectors.toMap(User::getUsername, User::getAddress));
        System.out.println(mapUser);
		
    }
}