Question

while implementing singleton as:

class MyConnection {
    private static MyConnection connection = new MyConnection();

    private MyConnection() {
    }

    public  static MyConnection getConnection() {
        return connection;
    }
}

1)why we give connection as static?

Is this only due to the fact that getConnection() is static and we cannot reference non-static in static context or there is any other reason?

2) is it necessary to declare connection as final?

Answer 1

1) why we give connection as static?

If it was non-static, you would need to have an instance of MyConnection to get hold of the connection reference which sort of defeats the purpose. 🙂

Is this only due to the fact that getConnection() is static and we cannot reference non-static in static context or there is any other reason?

Yes. (Since getConnection() needs to be static, connection needs to be static.)

2) is it necessary to declare connection as final?

No, but it’s good practice, since once initialized, it should not be changed.

But, an even better practice is to use an enum instead.

enum MyConnection {

    INSTANCE;

    // your methods...
}

and access it through MyConnection.INSTANCE.

Rule of thumb: If a class shall have a predefined number of instances, use an enum. In this case the number of instances is one.