I want to build a Java application to access the OpenStack services like the Identity Service (username, password, secret key, etc), Nova service (create and remove virtual
There is a project on github (CloudServiceDeployer) handling almost what you were asking for.
Take a more closer view to the classes below
There is java SDK(aka jcloud) is available to access the openstack functionality.
wiki link : https://wiki.openstack.org/wiki/OpenStack-SDK-Java