Class constructor call with class as input

Question

I'm working with a class and getting a call to this class with it as input.

 professor = new Professor(EEEE, AAAA, YEARS_90, DEP);

 depProf.addProfessor(professor)

Professor has a constructor of (String, String, Integer, String), but in a test I want to call it from another place with (Professor) as input.

public Professor(String name, String surname, Integer yearOfBirth, String department) {

    this.department = department;
    Person curPerson = new Person(name, surname, yearOfBirth);

}

How can I make a constructor of Professor(Professor)? If that make any sense.

I'm thinking about calling 1st constructor when second is called but don't actually know how to make it work.

You just write the constructor, what is confusing you specifically? `public Professor(Professor other) { ... }` and then copy his state or call the other constructor `this(other.getName(), other.getSurname(), other.getYearOfBirth(), other.getDepartment());` — Zabuzard, Sep 10 '20 at 19:28
Did you try searching the Internet for the words ___java copy constructor___ ? — Abra, Sep 10 '20 at 19:29
See also this answer to "How do I call one constructor from another in Java?" https://stackoverflow.com/questions/285177/how-do-i-call-one-constructor-from-another-in-java/15348070#15348070 — Christian Fries, Sep 10 '20 at 19:32
My problem with that is Professor only have department. Name, surname and year are inputs for another class, I can't use this.name cause it will be like Person.name and I don't want to call the object made by Professor — Rancio, Sep 10 '20 at 19:54

score 5 · Accepted Answer · answered Sep 10 '20 at 19:29

5

You can call another constructor in the same class for example:

public Professor(String name, String surname, Integer yearOfBirth) {
   this.name = name;
   this.surname = surname;
   this.yearOfBirth = yearOfBirth;
}

public Professor(String name, String surname, Integer yearOfBirth, String department) {
  this(name, surname, yearOfBirth);
  this.department = department;
}

public Professor(Professor p) {
  this(p.name, p.surname, p.yearOfBirth, p.department);
}

answered Sep 10 '20 at 19:29

k1r0

542
1
5
12

What if my Professor class doesn't actually have name, surname and yearOfBirth? Professor constructor calls Person(String, String, Integer) Professor only have department. – Rancio Sep 10 '20 at 19:51
Nevermind, didn't think about the superclass thingy. – Rancio Sep 10 '20 at 20:16

score 1 · Answer 2 · answered Sep 10 '20 at 19:29

1

You can use this to call another constructor.

public Professor(Professor professor) {
    this(professor.name, professor.surname, professor.yearOfBirth, professor.department);
}

answered Sep 10 '20 at 19:29

Unmitigated

76,500
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score 0 · Answer 3 · answered Sep 10 '20 at 19:29

0

If I get this right, you are trying to use a copy constructor. This constructor is generated by default in C++, but you have to manually implement one in Java, in your Professor class :

public Professor(Professor p) { 
    this(p.name, p.surname, p.yearOfBirth, p.department);
}

answered Sep 10 '20 at 19:29

Clémence CHOMEL

1

1

Note that C++ does not generate _such_ a constructor. It is different. More similar to Javas `clone` mechanism - black voodoo magic. – Zabuzard Sep 10 '20 at 19:32

Class constructor call with class as input

3 Answers3