Question

In the following code

public class Test {

    public static void main(String[] args){
        int [] arr = new int[]{1,2};
        String b=new String("abc");
        f(b,arr);
        System.out.println(b);
        System.out.println(arr[0]);

    }

    public static void f(String b, int[] arr){

        b+="de";
        b=null;
        arr[0] = 5;
    }
}

Why the reference variable of the string doesn’t behave like the reference variable of the array?.
I know string are immutable so operations on them creates new string but how about references to strings and how the reference b still refer to the old value although it was changed to refer to something else in f() method.

Answer 1

Object references in Java are passed by value. Assigning just changes the value, it does not alter the original object reference.

In your example arr[0] is changed, but try arr=null and you will see it has no effect after the method has returned.