Function that swaps two integers

Question

Possible Duplicate:
How to write a basic swap function in Java

Hi. I don't know java at all, and in the near future have no wish to study it. However I have lots of friends that are java programmers and from conversations I learnt that there is no analog of C#'s ref keyword in Java. Which made me wonder how can one write a function that swaps two integers in Java. My friends (though not very good java experts) could not write such a function. Is it officially impossible? Please note, that I understand that one can swap two integers without a function, the question is exactly to write a function that takes two integers and swaps them. Thanks in advance.

By "integer" do you mean "int" or "Integer"? One is a primitive, the other is a class. — Steve Emmerson, Oct 10 '10 at 19:31
@Steve: well, if it does make a difference, I would like to have an answer for both cases — Armen Tsirunyan, Oct 10 '10 at 19:32
Duplicate of : http://stackoverflow.com/questions/3624525/how-to-write-a-basic-swap-function-in-java/3624547 — codaddict, Oct 10 '10 at 19:34
@codaddict: I agree it's a duplicate. What should I do? Remove the thread? — Armen Tsirunyan, Oct 10 '10 at 19:35
no, let us close it as a duplicate (1 more close vote remaining) — Bozho, Oct 10 '10 at 19:38

score 4 · Accepted Answer · answered Oct 10 '10 at 19:32

Short: You can't.

Long: You need some workaround, like wrapping them in a mutable datatype, e.g. array, e.g.:

public static void swap(int[] a, int[] b) {
    int t = a[0]; a[0] = b[0]; b[0] = t;
}

but that doesn't have the same semantic, since what you're swapping is actually the array members, not the a and b themselves.

score 4 · Answer 2 · answered Oct 10 '10 at 19:34

In Java, all the arguments are passed by value. So there is no such thing as a ref.

However, you might achieve variable swapping by wapping values in objects (or arrays).

public class Holder<T> {
  public T value = null;
  public Holder(T v) { this.value = v; }
}

public static <T> void swap(Holder<T> a, Holder<T> b) {
  T temp = a.value; a.value = b.value; b.value = temp;
}

Function that swaps two integers

2 Answers2