If you live in New South Wales (and you intend to lodge Form J with the VFS office in Sydney), then you cannot sign Form J in front of a justice of the peace. As a NSW resident, Form J must be attested by a notary public. This means you must sign Form J in front of a notary public who will verify your identity and witness your signature.
Form J is required when you have changed your appearance. Sometimes you may have aged (ie, matured) especially if your previous passport photograph was taken when you were a child. Sometimes it's because you previously wore a turban but no longer wear a turban (or you previously didn't but now you do). For some, it's because they've changed their hairstyle or facial hair. Whatever the case may be, if you think you might look different now from what you do (or did before) in your passport photograph, then you may need to submit Form J with whatever other documents you intended to file with VFS.
As a leading provider of notary public services in Sydney, we help many clients with notarising Form J. If you also need help, you must make an appointment, bring your completed Form J with your photograph, and you must sign it in front of our notary public. Our notary public will verify your identity according to your photo identity (ie, passport or driver licence) and witness you sign Form J.