Random text

[DevShivmohan]

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinTable(name = "student_course",
        joinColumns = @JoinColumn(name = "student_id", referencedColumnName = "id"),
        inverseJoinColumns = @JoinColumn(name = "course_id", referencedColumnName = "id"))
    private Set<Course> courses = new HashSet<>();

    // Getters and setters
}

@Entity
public class Course {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    @ManyToMany(mappedBy = "courses")
    private Set<Student> students = new HashSet<>();

    // Getters and setters
}

@Service
public class MyService {
    @Autowired
    private StudentRepository studentRepository;

    @Autowired
    private CourseRepository courseRepository;

    public void addStudentToCourse(Long studentId, Long courseId) {
        Optional<Student> studentOptional = studentRepository.findById(studentId);
        Optional<Course> courseOptional = courseRepository.findById(courseId);

        if (studentOptional.isPresent() && courseOptional.isPresent()) {
            Student student = studentOptional.get();
            Course course = courseOptional.get();

            student.getCourses().add(course);
            course.getStudents().add(student);

            studentRepository.save(student);
            courseRepository.save(course);
        }
    }
}

``

[DevShivmohan]

Rahul query

@rahulmech12 @anuragrawat7

• Here is the list inside the parent list has multiple list and inside the sublist has multiple values so we have to print the anyone element from any sub list

  List<List<String>> listStrings = new ArrayList<>();
      listStrings.add(List.of("Sh","Moh","Rahul"));
      listStrings.add(List.of("Anu","Anuraga","Rahula"));
      String value = listStrings.stream().findFirst().get().stream().findFirst().get();
      System.out.println(value);

• Here is the list has multiple values so we have to find get any single value

  
  List<String> list = List.of("Sh","Moh","Rahul");
      String valueWithDefault = list.stream().findFirst().orElse("default value"); // if not any values in the list then it return default
      String value = list.stream().findFirst().get();
      System.out.println(valueWithDefault);
      System.out.println(value);