Stream流分组

将List集合泛型为对象中按照相同的成员属性值进行分组（Map集合）

示例代码

实体类：

@Data
public class Student implements Serializable {
    private Long id;
    private String name;
    private Integer age;
    private String sex;
}

持久层：

public interface Student implements Serializable {
    List<Student> findByStudent();
}

<select id="findByStudent" resultType>
    select * from student
</select>

业务层：

@Service
public class StudentServiceImpl{
    public void show(){
        List<Student> findByStudent = student.findByStudent(sysids);
        Map<String, List<Student>> groupBy = findByStudent.stream().collect(Collectors.groupingBy(Student::getName));
     }
}