Get Customer Status using Java API

I’m development an add-on for Jira Service Desk, using more rest api, because we can’t obtain the data that we need using java API.
This causes a slowdown of application and some times the screen is freezed caused by Rest calls are cancelled.

In order to improvement our add-on we need to access to the statuses of a request type by java doc. We can get the statuses of the workflow associated to issuetype of the request type, but not to statuses view by customer on the portal.

Is there an approach using java doc?