can you elaborate how will an application architecture(especially a Java one) would generally fit in an enterprise architecture?
A Java-based application architecture is for an application. The application is a software application, it can be an application that is included in an "enterprise" architecture. In this scenario, it could be referred to as an enterprise application.
However, an "enterprise architecture" is the blueprint for an "enterprise." There are many, many things involved, business processes, humans, organizations, financial resources, hardware, software applications, operating systems, suppliers, partners, regulations, etc.