I assume you are referring to the documentation link below with this question. The answer would depend on exactly what you are trying to accomplish, but for the most part yes it would require A2A. The External API is also available and it may be possible to create a custom API based solution depending on the exact requirements you may have, but this is not guaranteed to meet your needs and would also likely be a lot more work than following the A2A procedure that is documented below. It should also be noted that if you choose to make a custom API based solution this would not be covered by CA Support since it would be a customization.
Documentation for A2A with Java App:
Integrate a Java Application or Application Server - CA Privileged Access Manager - 3.2 - CA Technologies Documentation
Documentation on API:
External API for Integrating Applications - CA Privileged Access Manager - 3.2 - CA Technologies Documentation
Hope this helps,
Christian Lutz
Sr. Support Engineer
CA Technologies - North America