Swap two numbers in Java

Asked Aug 24 '19 at 09:07

Active Aug 24 '19 at 09:07

Viewed 168 times

Can anyone explain to me why this swap method doesn't swap two numbers?

public class Test {

public static void main(String[] arr) {
    int original1 = 5;
    int original2 = 10;
    swap(original1, original2);
    System.out.println(original1);
    System.out.println(original2);
}

static void swap(int a, int b){
    int temp = a;
    a=b;
    b=temp;
}}

asked Aug 24 '19 at 09:07

JohnPix

1,595
21
44

because you swap them in different scopes – Youcef LAIDANI Aug 24 '19 at 09:10
2

https://stackoverflow.com/questions/40480/is-java-pass-by-reference-or-pass-by-value – Martin Tarjányi Aug 24 '19 at 09:11
2

Essentially, the two ints are copied and in the swap method you swap the copied variables, not the original ones. – Martin Tarjányi Aug 24 '19 at 09:12
tl;dr: since java has pass-by-value semantics, you cannot do what you want to do with primitives. You can do this, however, with arrays. – Turing85 Aug 24 '19 at 09:15
1

The above code is following the calling convention of "Call By Value". So basically you are passing values, not references. Hence its not changed. – Dibsyhex Aug 24 '19 at 09:27

Swap two numbers in Java

0 Answers0