`Arrays,copyOf` didn't do a deep copy of objects as it is supposed to

Question

I have classBook which can have many Authors. I pass few objects of class Author to the constructor of class Book then copy these objects by Arrays.copyOF but then if I change any Author data outside the object it will change everywhere so it means the copy has not been created.

I would like to create deep copy. Code is compiling and running with no errors.

import java.util.Arrays;

public class Book {
    private String tytul;
    private int rokWydania;
    private Author[] autorzy;

    public Book(String tytul, int rokWydania, Author... autorzy) {
        this.tytul = tytul;
        this.rokWydania = rokWydania;
        this.autorzy = Arrays.copyOf(autorzy, autorzy.length);
    }

    public String toString() {
        String s = "      Tytuł: " + tytul +"\nrok wydania: " + rokWydania + "\n";
        if(autorzy.length == 1)
            s+="      Autor: " + autorzy[0];
        else{
            s+="    Autorzy: " + autorzy[0];
            for(int i = 1; i < autorzy.length; i++)
                s+="\n             " + autorzy[i];
        }       
        return s + "\n\n";
    }

    public static void main(String[] args) {
        Author a1 = new Author("Isabel", "Allende", 1942);
        Author a2 = new Author("Manueala", "Gretkowska", 1964);
        Author a3 = new Author("Piotr", "Pietucha", 1954);

        Book b1 = new Book("Suma naszych dni", 2010, a1);
        Book b2 = new Book("Polka", 2001, a2);
        Book b3 = new Book("Sceny z życia pozamałżeńskiego", 2003, a2, a3);

        a2.zmienInformacje("Tove", "Jansson", 1956);
        Book b4 = new Book("Lato muminków", 2006, a2);

        System.out.println(b1);

        System.out.println(b2);

        System.out.println(b3);

        System.out.println(b4);
    }
}

public class Author {
    private String imie, nazwisko;
    private int rokUrodzenia;

    public Author(String imie, String nazwisko, int rokUrodzenia) {
        this.imie = imie;
        this.nazwisko = nazwisko;
        this.rokUrodzenia = rokUrodzenia;
    }

    public String getImie() {
        return imie;
    }

    public String getNazwisko() {
        return nazwisko;
    }

    public int getRokUrodzenia() {
        return rokUrodzenia;
    }

    @Override
    public String toString() {
        return  imie + " " + nazwisko + " (ur. " + rokUrodzenia + ")";
    }

    public void zmienInformacje(String imie, String nazwisko, int rokUrodzenia) {
        this.imie = imie;
        this.nazwisko = nazwisko;
        this.rokUrodzenia = rokUrodzenia;

    }

}

Desired output:

     Tytuł: Suma naszych dni
  rok wydania: 2010
        Autor: Isabel Allende (ur. 1942)


        Tytuł: Polka
  rok wydania: 2001
        Autor: Manuela Gretkowska (ur. 1964)


        Tytuł: Suma naszych dni
  rok wydania: 2010
      Autorzy: Manuela Gretkowska (ur. 1964)   
               Piotr Pietucha (ur. 1954)


        Tytuł: Lato muminków
  rok wydania: 2006
        Autor: Tove Jansson (ur. 1956)

My output

      Tytuł: Suma naszych dni
rok wydania: 2010
      Autor: Isabel Allende (ur. 1942)


      Tytuł: Polka
rok wydania: 2001
      Autor: Tove Jansson (ur. 1956)//WRONG


      Tytuł: Sceny z życia pozamałżeńskiego
rok wydania: 2003
    Autorzy: Tove Jansson (ur. 1956)//WRONG
             Piotr Pietucha (ur. 1954)


      Tytuł: Lato muminków
rok wydania: 2006
      Autor: Tove Jansson (ur. 1956)

Did it say it was going to? Probably not. So change the title to reflect the goal (and *search* for it) - e.g. "Create a deep copy of an Array" — user2246674, May 19 '13 at 19:35
@user2246674 Yes it did, there is whole other subject about it. — Yoda, May 19 '13 at 19:35
Nope, [it doesn't say it will make a deep copy](http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#copyOf(T%5B%5D,%20int)). There *is* a whole subject on this task - of which there are many existing answers/approaches. (e.g. [1](http://stackoverflow.com/questions/64036/how-do-you-make-a-deep-copy-of-an-object-in-java), [2](http://stackoverflow.com/questions/3947227/deep-copy-of-an-object-array)) — user2246674, May 19 '13 at 19:37
@user2246674 But please do not be mean here. In my other subject there was whole discussion about valueOf sot this is not obvious. Thank you. — Yoda, May 19 '13 at 19:46
Robert, if the Javadoc of a method doesn't say it will perform a deep copy, it is simply a mistake on your part to assert that 'it is supposed to' do so. No amount of hand-waving or subject-changing or referring to uncited other topics can obscure that. Not a real question. — user207421, May 19 '13 at 23:41

score 1 · Answer 1 · answered May 19 '13 at 20:00

1

I think Arrays.copyOf is working fine. Issue is in line a2.zmienInformacje("Tove", "Jansson", 1956); you are updating Author a2 before printing Book b2 and b3 .

answered May 19 '13 at 20:00

Peeyush

422
3
13

You are right, but the problem is that teacher of my student does not understand `agregation` correctly. She missunderstands it with `composition`, altough she cannot implement any of these correctly so I have to do it "her way". – Yoda May 19 '13 at 22:31
1

You're avoiding the issue. The only visible problem here is that you are attributing properties to `Arrays.copyOf()` that it does not have. – user207421 May 20 '13 at 01:25

`Arrays,copyOf` didn't do a deep copy of objects as it is supposed to

1 Answers1