Why output is not 16?

Question

I am using parameter passing. but I use return type for the program. but the output is not return value, it shows assigned value. y ?

public class Program
{
public static void main(String[] args) {
int x=4;
square(x);
System.out.println(x);
}
static int square(int x){
x=x*x;
return x;
}
}

Answer 1

You need to use x = square(x); instead of square(x); as this doesn't change the value of variable of data type int.

Answer 2

in java primitive variables are passed by value (a copy is created and changes on that copy don't affect the original variable.
Objects are intead passed by referenve.