Question

public class Test {

    public static void change(char[] a){
        a[0] = '1';
        a[1] = '2';
    }

    public static void main(String args[]){
        char[] a = new char[]{'a','b'};

        change(a);

        System.out.println(a);
    }

}

The output is 12

public class Test {

    public static void change(char[] a){
        a = new char[]{'1','2'};
    }

    public static void main(String args[]){
        char[] a = new char[]{'a','b'};

        change(a);

        System.out.println(a);
    }

}

The output is ab. I understand I am missing something about the way java passes method arguments. I understand references to objects are passed by value. However, I cannot reconcile what I understand with the results of these programs.

Answer 1

In version “2”, the change method “does nothing”, because you are assigning a new array to a, which is the the local (parameter) variable a. This has no effect on the array assigned to variable a declared in the main method.

The new array goes out of scope and is inaccessible (and thus earmarked for garbage collection) when the change() method completes.