The OC files a suit seeking judgment, but not a judgment. Judgments are made by a court.
Do you have a court-ordered judgment? The issue of jurisdiction should have been settled in the lawsuit and court proceedings, of which you should have received advance notice, and notice of any court order.
I have a court ordered judgement. I don't recall ever having a notice forwarded to me, I certainly never received a notice at my PA address. It is indeed a valid judgement but I never recall having gotten a court order.
The issue is whether or not you were properly served.
Sounds like they couldn't find you, so they either served you at your last known address, or by publication in a newspaper or something like that. Look up the NJ laws on this, then call the court and find out how the plaintiff said you were served, and then determine whether the method they used matches up with what the actually did.
If it doesn't match up, then you may have a basis for a motion to vacate. They only have kind of a limited responsiblity to track you down when you go off the grid.