Question

Can anybody explain me why below code is working on private member variable?

    public class Person implements Comparable<Person> {
    private String firstName;
    public Person(String firstName) {
        this.firstName = firstName;
        }

    @Override
    public int compareTo(Person o) {
        return firstName.compareToIgnoreCase(o.firstName);  // why does it work?    }    }
    }
}

EDIT Why o.firstName is getting compile ? where firstName is private variable.

Answer 1

The access modifiers control access per class rather than per instance. So, methods of class T can access all members (even private) of other class T‘s instances.

The Access Control from JLS 7 link for the curious. It says, “Note that accessibility is a static property that can be determined at compile time; it depends only on types and declaration modifiers.”