How to swap two objects in Java?

Question

I have a class written for Fraction objects. I need to swap two Fraction objects, not the contents of the objects. Here is my code.

public void fswap(Fraction other){
    Fraction temp = other.copy();
    other = this;
    this = temp;

The copy() method returns a Fraction object identical to the object it was called on. The last line of this code throws an error in my IDE "cannot assign a value to final variable this". Any help is greatly appreciated.

just curious - why do you need this? why not just swap the content? — Iłya Bursov, Dec 04 '15 at 22:15
Do you mean, swap the _variables_ that refer to those objects, so that `a` becomes `b` and `b` becomes `a`? I'm not sure what it would mean to swap the actual objects. — Dawood ibn Kareem, Dec 04 '15 at 22:22

Louis Wasserman · Accepted Answer · 2015-12-04T22:14:30.437

5

You cannot write a swap method in Java that swaps the objects, not their contents. It is literally impossible. This is a distinguishing feature of a pass-by-value language, though it's always important to remember that Java passes references by value.

edited Dec 04 '15 at 22:14

answered Dec 04 '15 at 22:13

Louis Wasserman

191,574
25
345
413

1

maybe worth noting that Java is in fact pass by value despite its ability to pass objects without copying. – djechlin Dec 04 '15 at 22:14

How to swap two objects in Java?

1 Answers1