How to make a relation between two objects in database JAVA
I am currently trying to create a relation between my Student class and my Discipline class. This is what I am doing:
@Service
public class StudentRegistrationService implements ApplicationRunner {
private final StudentRepository repository;
private final DisciplineRepository repository1;
public StudentRegistrationService(StudentRepository repository, DisciplineRepository repository1) {
this.repository = repository;
this.repository1 = repository1;
}
@Override
public void run(ApplicationArguments args) throws Exception {
Scanner scanner = new Scanner(System.in);
while (true) {
String input = scanner.nextLine();
String split = input.split(" ");
String command = split[0];
switch (command.toUpperCase()) {
case "END":
System.out.println("bye bye");
return;
case "STUDLIST":
printAllStudents();
break;
case "STUDNEW":
String studentDetails = Arrays.copyOfRange(split, 1, split.length);
createNewStudent(studentDetails);
break;
case "DISCLIST":
printAllDisciplines();
break;
case "DISCNEW":
String disciplineDetails = Arrays.copyOfRange(split, 1, split.length);
createNewDiscipline(disciplineDetails);
break;
case "STUDDISC":
String studentAndDisciplineId = Arrays.copyOfRange(split, 1, split.length);
studendAndDiscipline(studentAndDisciplineId);
break;
default:
System.out.println("UNKNOWN command, try again!");
break;
}
}
}
private void createNewDiscipline(String details) {
int hours=Integer.parseInt(details[1]);
repository1.save(new Discipline(details[0],hours));
}
private void printAllDisciplines() {
Iterable<Discipline> allDisciplines = repository1.findAll();
for (Discipline discipline : allDisciplines) {
System.out.println(discipline);
}
}
private void createNewStudent(String details) {
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd.MM.yyyy");
LocalDate localDate = LocalDate.parse(details[1], dtf);
repository.save(new Student(details[0],localDate));
}
private void printAllStudents() {
Iterable<Student> allStudents = repository.findAll();
for (Student student : allStudents) {
System.out.println(student);
}
}
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
}
In studentAndDiscipline I have to create a relation between a student and a discipline both by ID, but I am doing it wrong. I tried using Optional<>, but it doesn't work either.
My Student class:
@Entity
class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
private LocalDate enrollmentDate;
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
List<Discipline> disciplines;
private Student() {
// Required by Hibernate
}
public Student(String name, LocalDate enrollmentDate) {
this.name = name;
this.enrollmentDate = enrollmentDate;
}
void addDiscipline(Discipline discipline) {
this.disciplines.add(discipline);
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + ''' +
", enrollmentDate=" + enrollmentDate +
", disciplines=" + disciplines +
'}';
}
}
My Discipline Class:
@Entity
class Discipline {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
String name;
int credits;
private Discipline() {
// Required by Hibernate
}
public Discipline(String name, int credits) {
this.name = name;
this.credits = credits;
}
@Override
public String toString() {
return "Discipline{" +
"id=" + id +
", name='" + name + ''' +
", credits=" + credits +
'}';
}
}
My StudentRepository:
interface StudentRepository extends CrudRepository<Student, Integer> {
}
My DisciplineRepository:
interface DisciplineRepository extends CrudRepository<Discipline, Integer> {
}
java database oop
add a comment |
I am currently trying to create a relation between my Student class and my Discipline class. This is what I am doing:
@Service
public class StudentRegistrationService implements ApplicationRunner {
private final StudentRepository repository;
private final DisciplineRepository repository1;
public StudentRegistrationService(StudentRepository repository, DisciplineRepository repository1) {
this.repository = repository;
this.repository1 = repository1;
}
@Override
public void run(ApplicationArguments args) throws Exception {
Scanner scanner = new Scanner(System.in);
while (true) {
String input = scanner.nextLine();
String split = input.split(" ");
String command = split[0];
switch (command.toUpperCase()) {
case "END":
System.out.println("bye bye");
return;
case "STUDLIST":
printAllStudents();
break;
case "STUDNEW":
String studentDetails = Arrays.copyOfRange(split, 1, split.length);
createNewStudent(studentDetails);
break;
case "DISCLIST":
printAllDisciplines();
break;
case "DISCNEW":
String disciplineDetails = Arrays.copyOfRange(split, 1, split.length);
createNewDiscipline(disciplineDetails);
break;
case "STUDDISC":
String studentAndDisciplineId = Arrays.copyOfRange(split, 1, split.length);
studendAndDiscipline(studentAndDisciplineId);
break;
default:
System.out.println("UNKNOWN command, try again!");
break;
}
}
}
private void createNewDiscipline(String details) {
int hours=Integer.parseInt(details[1]);
repository1.save(new Discipline(details[0],hours));
}
private void printAllDisciplines() {
Iterable<Discipline> allDisciplines = repository1.findAll();
for (Discipline discipline : allDisciplines) {
System.out.println(discipline);
}
}
private void createNewStudent(String details) {
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd.MM.yyyy");
LocalDate localDate = LocalDate.parse(details[1], dtf);
repository.save(new Student(details[0],localDate));
}
private void printAllStudents() {
Iterable<Student> allStudents = repository.findAll();
for (Student student : allStudents) {
System.out.println(student);
}
}
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
}
In studentAndDiscipline I have to create a relation between a student and a discipline both by ID, but I am doing it wrong. I tried using Optional<>, but it doesn't work either.
My Student class:
@Entity
class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
private LocalDate enrollmentDate;
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
List<Discipline> disciplines;
private Student() {
// Required by Hibernate
}
public Student(String name, LocalDate enrollmentDate) {
this.name = name;
this.enrollmentDate = enrollmentDate;
}
void addDiscipline(Discipline discipline) {
this.disciplines.add(discipline);
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + ''' +
", enrollmentDate=" + enrollmentDate +
", disciplines=" + disciplines +
'}';
}
}
My Discipline Class:
@Entity
class Discipline {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
String name;
int credits;
private Discipline() {
// Required by Hibernate
}
public Discipline(String name, int credits) {
this.name = name;
this.credits = credits;
}
@Override
public String toString() {
return "Discipline{" +
"id=" + id +
", name='" + name + ''' +
", credits=" + credits +
'}';
}
}
My StudentRepository:
interface StudentRepository extends CrudRepository<Student, Integer> {
}
My DisciplineRepository:
interface DisciplineRepository extends CrudRepository<Discipline, Integer> {
}
java database oop
add a comment |
I am currently trying to create a relation between my Student class and my Discipline class. This is what I am doing:
@Service
public class StudentRegistrationService implements ApplicationRunner {
private final StudentRepository repository;
private final DisciplineRepository repository1;
public StudentRegistrationService(StudentRepository repository, DisciplineRepository repository1) {
this.repository = repository;
this.repository1 = repository1;
}
@Override
public void run(ApplicationArguments args) throws Exception {
Scanner scanner = new Scanner(System.in);
while (true) {
String input = scanner.nextLine();
String split = input.split(" ");
String command = split[0];
switch (command.toUpperCase()) {
case "END":
System.out.println("bye bye");
return;
case "STUDLIST":
printAllStudents();
break;
case "STUDNEW":
String studentDetails = Arrays.copyOfRange(split, 1, split.length);
createNewStudent(studentDetails);
break;
case "DISCLIST":
printAllDisciplines();
break;
case "DISCNEW":
String disciplineDetails = Arrays.copyOfRange(split, 1, split.length);
createNewDiscipline(disciplineDetails);
break;
case "STUDDISC":
String studentAndDisciplineId = Arrays.copyOfRange(split, 1, split.length);
studendAndDiscipline(studentAndDisciplineId);
break;
default:
System.out.println("UNKNOWN command, try again!");
break;
}
}
}
private void createNewDiscipline(String details) {
int hours=Integer.parseInt(details[1]);
repository1.save(new Discipline(details[0],hours));
}
private void printAllDisciplines() {
Iterable<Discipline> allDisciplines = repository1.findAll();
for (Discipline discipline : allDisciplines) {
System.out.println(discipline);
}
}
private void createNewStudent(String details) {
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd.MM.yyyy");
LocalDate localDate = LocalDate.parse(details[1], dtf);
repository.save(new Student(details[0],localDate));
}
private void printAllStudents() {
Iterable<Student> allStudents = repository.findAll();
for (Student student : allStudents) {
System.out.println(student);
}
}
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
}
In studentAndDiscipline I have to create a relation between a student and a discipline both by ID, but I am doing it wrong. I tried using Optional<>, but it doesn't work either.
My Student class:
@Entity
class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
private LocalDate enrollmentDate;
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
List<Discipline> disciplines;
private Student() {
// Required by Hibernate
}
public Student(String name, LocalDate enrollmentDate) {
this.name = name;
this.enrollmentDate = enrollmentDate;
}
void addDiscipline(Discipline discipline) {
this.disciplines.add(discipline);
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + ''' +
", enrollmentDate=" + enrollmentDate +
", disciplines=" + disciplines +
'}';
}
}
My Discipline Class:
@Entity
class Discipline {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
String name;
int credits;
private Discipline() {
// Required by Hibernate
}
public Discipline(String name, int credits) {
this.name = name;
this.credits = credits;
}
@Override
public String toString() {
return "Discipline{" +
"id=" + id +
", name='" + name + ''' +
", credits=" + credits +
'}';
}
}
My StudentRepository:
interface StudentRepository extends CrudRepository<Student, Integer> {
}
My DisciplineRepository:
interface DisciplineRepository extends CrudRepository<Discipline, Integer> {
}
java database oop
I am currently trying to create a relation between my Student class and my Discipline class. This is what I am doing:
@Service
public class StudentRegistrationService implements ApplicationRunner {
private final StudentRepository repository;
private final DisciplineRepository repository1;
public StudentRegistrationService(StudentRepository repository, DisciplineRepository repository1) {
this.repository = repository;
this.repository1 = repository1;
}
@Override
public void run(ApplicationArguments args) throws Exception {
Scanner scanner = new Scanner(System.in);
while (true) {
String input = scanner.nextLine();
String split = input.split(" ");
String command = split[0];
switch (command.toUpperCase()) {
case "END":
System.out.println("bye bye");
return;
case "STUDLIST":
printAllStudents();
break;
case "STUDNEW":
String studentDetails = Arrays.copyOfRange(split, 1, split.length);
createNewStudent(studentDetails);
break;
case "DISCLIST":
printAllDisciplines();
break;
case "DISCNEW":
String disciplineDetails = Arrays.copyOfRange(split, 1, split.length);
createNewDiscipline(disciplineDetails);
break;
case "STUDDISC":
String studentAndDisciplineId = Arrays.copyOfRange(split, 1, split.length);
studendAndDiscipline(studentAndDisciplineId);
break;
default:
System.out.println("UNKNOWN command, try again!");
break;
}
}
}
private void createNewDiscipline(String details) {
int hours=Integer.parseInt(details[1]);
repository1.save(new Discipline(details[0],hours));
}
private void printAllDisciplines() {
Iterable<Discipline> allDisciplines = repository1.findAll();
for (Discipline discipline : allDisciplines) {
System.out.println(discipline);
}
}
private void createNewStudent(String details) {
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd.MM.yyyy");
LocalDate localDate = LocalDate.parse(details[1], dtf);
repository.save(new Student(details[0],localDate));
}
private void printAllStudents() {
Iterable<Student> allStudents = repository.findAll();
for (Student student : allStudents) {
System.out.println(student);
}
}
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
}
In studentAndDiscipline I have to create a relation between a student and a discipline both by ID, but I am doing it wrong. I tried using Optional<>, but it doesn't work either.
My Student class:
@Entity
class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name;
private LocalDate enrollmentDate;
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
List<Discipline> disciplines;
private Student() {
// Required by Hibernate
}
public Student(String name, LocalDate enrollmentDate) {
this.name = name;
this.enrollmentDate = enrollmentDate;
}
void addDiscipline(Discipline discipline) {
this.disciplines.add(discipline);
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + ''' +
", enrollmentDate=" + enrollmentDate +
", disciplines=" + disciplines +
'}';
}
}
My Discipline Class:
@Entity
class Discipline {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
String name;
int credits;
private Discipline() {
// Required by Hibernate
}
public Discipline(String name, int credits) {
this.name = name;
this.credits = credits;
}
@Override
public String toString() {
return "Discipline{" +
"id=" + id +
", name='" + name + ''' +
", credits=" + credits +
'}';
}
}
My StudentRepository:
interface StudentRepository extends CrudRepository<Student, Integer> {
}
My DisciplineRepository:
interface DisciplineRepository extends CrudRepository<Discipline, Integer> {
}
java database oop
java database oop
edited Nov 20 '18 at 2:15
Nikola Hristov
asked Nov 20 '18 at 0:47
Nikola HristovNikola Hristov
83
83
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
Discipline discipline=repository1.findById(disciplineId);
, is not right. findById(ID id)
would return Optional<T>
type, you need to use get()
to get the T.
And you should make sure discipline is not null. At least you need to check it like
Student student=repository.findById(studentId).get();
Discipline discipline=repository1.findById(disciplineId).get();
if (discipline != null) {
student.addDiscipline(discipline);
System.out.println("Adding discipline to student.");
}
If you are sure discipline is not null, you need to check addDiscipline() implementation.
The problem is that the program doesn't compile at all. At Student student and Discipline discipline I get incompatible types. Student student says required Student, found Optional and Discipline discipline says required Discipline, found optional.
– Nikola Hristov
Nov 20 '18 at 1:25
please add Student, Discipline and StudentRepository
– Bejond
Nov 20 '18 at 1:51
I have added it to my original post. Thanks for helping me.
– Nikola Hristov
Nov 20 '18 at 2:16
updated answer.
– Bejond
Nov 20 '18 at 2:23
thanks a lot. It now compiles, but I get "ArrayIndexOutOfBoundsException: 2"
– Nikola Hristov
Nov 20 '18 at 3:15
|
show 1 more comment
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53384684%2fhow-to-make-a-relation-between-two-objects-in-database-java%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
Discipline discipline=repository1.findById(disciplineId);
, is not right. findById(ID id)
would return Optional<T>
type, you need to use get()
to get the T.
And you should make sure discipline is not null. At least you need to check it like
Student student=repository.findById(studentId).get();
Discipline discipline=repository1.findById(disciplineId).get();
if (discipline != null) {
student.addDiscipline(discipline);
System.out.println("Adding discipline to student.");
}
If you are sure discipline is not null, you need to check addDiscipline() implementation.
The problem is that the program doesn't compile at all. At Student student and Discipline discipline I get incompatible types. Student student says required Student, found Optional and Discipline discipline says required Discipline, found optional.
– Nikola Hristov
Nov 20 '18 at 1:25
please add Student, Discipline and StudentRepository
– Bejond
Nov 20 '18 at 1:51
I have added it to my original post. Thanks for helping me.
– Nikola Hristov
Nov 20 '18 at 2:16
updated answer.
– Bejond
Nov 20 '18 at 2:23
thanks a lot. It now compiles, but I get "ArrayIndexOutOfBoundsException: 2"
– Nikola Hristov
Nov 20 '18 at 3:15
|
show 1 more comment
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
Discipline discipline=repository1.findById(disciplineId);
, is not right. findById(ID id)
would return Optional<T>
type, you need to use get()
to get the T.
And you should make sure discipline is not null. At least you need to check it like
Student student=repository.findById(studentId).get();
Discipline discipline=repository1.findById(disciplineId).get();
if (discipline != null) {
student.addDiscipline(discipline);
System.out.println("Adding discipline to student.");
}
If you are sure discipline is not null, you need to check addDiscipline() implementation.
The problem is that the program doesn't compile at all. At Student student and Discipline discipline I get incompatible types. Student student says required Student, found Optional and Discipline discipline says required Discipline, found optional.
– Nikola Hristov
Nov 20 '18 at 1:25
please add Student, Discipline and StudentRepository
– Bejond
Nov 20 '18 at 1:51
I have added it to my original post. Thanks for helping me.
– Nikola Hristov
Nov 20 '18 at 2:16
updated answer.
– Bejond
Nov 20 '18 at 2:23
thanks a lot. It now compiles, but I get "ArrayIndexOutOfBoundsException: 2"
– Nikola Hristov
Nov 20 '18 at 3:15
|
show 1 more comment
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
Discipline discipline=repository1.findById(disciplineId);
, is not right. findById(ID id)
would return Optional<T>
type, you need to use get()
to get the T.
And you should make sure discipline is not null. At least you need to check it like
Student student=repository.findById(studentId).get();
Discipline discipline=repository1.findById(disciplineId).get();
if (discipline != null) {
student.addDiscipline(discipline);
System.out.println("Adding discipline to student.");
}
If you are sure discipline is not null, you need to check addDiscipline() implementation.
private void studendAndDiscipline(String details) {
int studentId=Integer.parseInt(details[1]);
int disciplineId=Integer.parseInt(details[2]);
Student student=repository.findById(studentId);
Discipline discipline=repository1.findById(disciplineId);
student.addDiscipline(discipline);
}
Discipline discipline=repository1.findById(disciplineId);
, is not right. findById(ID id)
would return Optional<T>
type, you need to use get()
to get the T.
And you should make sure discipline is not null. At least you need to check it like
Student student=repository.findById(studentId).get();
Discipline discipline=repository1.findById(disciplineId).get();
if (discipline != null) {
student.addDiscipline(discipline);
System.out.println("Adding discipline to student.");
}
If you are sure discipline is not null, you need to check addDiscipline() implementation.
edited Nov 20 '18 at 2:22
answered Nov 20 '18 at 1:08
BejondBejond
890515
890515
The problem is that the program doesn't compile at all. At Student student and Discipline discipline I get incompatible types. Student student says required Student, found Optional and Discipline discipline says required Discipline, found optional.
– Nikola Hristov
Nov 20 '18 at 1:25
please add Student, Discipline and StudentRepository
– Bejond
Nov 20 '18 at 1:51
I have added it to my original post. Thanks for helping me.
– Nikola Hristov
Nov 20 '18 at 2:16
updated answer.
– Bejond
Nov 20 '18 at 2:23
thanks a lot. It now compiles, but I get "ArrayIndexOutOfBoundsException: 2"
– Nikola Hristov
Nov 20 '18 at 3:15
|
show 1 more comment
The problem is that the program doesn't compile at all. At Student student and Discipline discipline I get incompatible types. Student student says required Student, found Optional and Discipline discipline says required Discipline, found optional.
– Nikola Hristov
Nov 20 '18 at 1:25
please add Student, Discipline and StudentRepository
– Bejond
Nov 20 '18 at 1:51
I have added it to my original post. Thanks for helping me.
– Nikola Hristov
Nov 20 '18 at 2:16
updated answer.
– Bejond
Nov 20 '18 at 2:23
thanks a lot. It now compiles, but I get "ArrayIndexOutOfBoundsException: 2"
– Nikola Hristov
Nov 20 '18 at 3:15
The problem is that the program doesn't compile at all. At Student student and Discipline discipline I get incompatible types. Student student says required Student, found Optional and Discipline discipline says required Discipline, found optional.
– Nikola Hristov
Nov 20 '18 at 1:25
The problem is that the program doesn't compile at all. At Student student and Discipline discipline I get incompatible types. Student student says required Student, found Optional and Discipline discipline says required Discipline, found optional.
– Nikola Hristov
Nov 20 '18 at 1:25
please add Student, Discipline and StudentRepository
– Bejond
Nov 20 '18 at 1:51
please add Student, Discipline and StudentRepository
– Bejond
Nov 20 '18 at 1:51
I have added it to my original post. Thanks for helping me.
– Nikola Hristov
Nov 20 '18 at 2:16
I have added it to my original post. Thanks for helping me.
– Nikola Hristov
Nov 20 '18 at 2:16
updated answer.
– Bejond
Nov 20 '18 at 2:23
updated answer.
– Bejond
Nov 20 '18 at 2:23
thanks a lot. It now compiles, but I get "ArrayIndexOutOfBoundsException: 2"
– Nikola Hristov
Nov 20 '18 at 3:15
thanks a lot. It now compiles, but I get "ArrayIndexOutOfBoundsException: 2"
– Nikola Hristov
Nov 20 '18 at 3:15
|
show 1 more comment
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53384684%2fhow-to-make-a-relation-between-two-objects-in-database-java%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown