Does Java Pass Primitives by Reference?

Pass by Reference for Primitives in Java

Java employs pass by value, unlike C , which utilizes pass by reference. This can create scenarios where modifying a primitive data type (e.g., int, float) in a method doesn't affect its value outside the method.

Consider this Java code:

public class XYZ {
    public static void main() {
        int toyNumber = 5;
        XYZ temp = new XYZ();
        temp.play(toyNumber);
        System.out.println("Toy number in main " + toyNumber);
    }

    void play(int toyNumber) {
        System.out.println("Toy number in play " + toyNumber);
        toyNumber++;
        System.out.println("Toy number in play after increment " + toyNumber);
    }
}

This code prints:

Toy number in play 5
Toy number in play after increment 6
Toy number in main 5

The toyNumber variable is not modified outside the play() method because it is passed by value.

Alternatives to Pass by Reference in Java:

To mimic C pass by reference in Java for primitives, several options are available:

1. Public Member Variable:

Create a class with a public member variable for toyNumber, and pass a reference to the class.

class MyToy {
    public int toyNumber;
}

void play(MyToy toy) {
    System.out.println("Toy number in play " + toy.toyNumber);
    toy.toyNumber++;
    System.out.println("Toy number in play after increment " + toy.toyNumber);
}

2. Return Value:

Instead of pass by reference, return the modified value from the method.

int play(int toyNumber) {
    System.out.println("Toy number in play " + toyNumber);
    toyNumber++;
    System.out.println("Toy number in play after increment " + toyNumber);
    return toyNumber;
}

In the main method, update toyNumber using the returned value.

3. Class/Static Variable:

If the play() and main() methods are part of the same class, convert toyNumber to a class member variable.

4. Array of One Element:

This is a hack but entails passing a single-element array and modifying its value.

void play(int[] toyNumber) {
    System.out.println("Toy number in play " + toyNumber[0]);
    toyNumber[0]++;
    System.out.println("Toy number in play after increment " + toyNumber[0]);
}

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