Why use private modifier for immutable final instance var?

class InterfaceExample{
    public static void main (String... args){
        MyInterface[] = {new ImplOne, new ImplTwo};

        for (MyInterface i : iList) {
            System.out.println(i.getString());
        }
    }
}

interface MyInterface{
    public String getString();
}

class ImplOne implements MyInterface{
    @Override
    public String getString(){ return "Who am I?"; }
}

class ImplTwo implements MyInterface{
    @Override
    public String getString(){ return "I am YOU."; }
}