integration with java application
This is a discussion forum BETWEEN AutoCAD users and this particular forum is dedicated to AutoCAD VBA/COM API discussion. Anyone posts here, questions or replies, are AutoCAD users. You do not but Autodesk's applications here.
Your question may or may not have anythign to do with AutoCAD VBA/COP API, depending on what your Java application does, and how you want it to be integrated with AutoCAD.
So, either you describe in more details on what your app does and what you expect the integration is and why you think it could have anything to do with AutoCAD COM API/VBA, so, someone may offer opinions; or you should find better/suitable place to ask question. Maybe, you first need to find a qualified Autodesk consultant (often a good Autodesk resaler would do) to gives you some direction before diving into your integration thing.
Again, your description is very vague in terms of "integration".
What kind of application (written in Java) is yours? Desktop app, web app, Windows services, or backend services...? How do you want it to interact with AutoCAD application (an heavy desktop UI application)? or you only need to interact/have access with/to data in DWG file, not necessarily with AutoCAD application itself. For the former, you need to have AutoCAD installed and minimum user interaction is often necessary; for the latter, you may want to look into Autodesk's Forge Cloud services, or license RealDWG technology.
It seems you really need to find someone who knows AutoCAD line of products/technologies well to gives some ideas before you can ask concrete questions suitable to this forum (AutoCAD VBA/COM APIs).