No, Unfortunately, We don’t have any out of the box Java based Developer Portal. You can build one using our Management APIs. Some of our customers did same. They do have developer portal built on java but they are custom built using Management APIs.
We have two kinds of Developer Portals. 1. Drupal - PHP based Developer Portal. 2. Apigee Edge New Developer Portals - Out of the box - Light Weight Portals.
You do get multiple portal instances with own branding with Drupal / Light weight out of the box Apigee Edge new portals.
I would suggest to go with Drupal based portals instead of re-inventing the wheel with Java based one.
Hope it helps someone looking for same. Keep us posted if you have any queries.