Reference Passing

Reference passing allows variable to be modified by the function it's passed to.

Passing By Value

Primitive types (int, double etc...) and Strings are passed by value.

Let's look at the following example:

public class Main { public static void main(String[] args) { int num = 0; incrementValue(num); System.out.print(num); } static void incrementValue(int num) { num++; } }

Output:

0

num is incremented by 1 in theincrementValue function. Since it's passed by value it remains 0 in the main function.

Passing By Reference

Arrays and objects are always passed by reference.

public class Main { public static void main(String[] args) { int[] arr = { 1, 2 }; modifyArray(arr); System.out.print(arr[0] + " " + arr[1]); } static void modifyArray(int[] arrayArg) { arrayArg[0] = 3; arrayArg[1] = 4; } }

Output:

3 4