How to get usage of quotas with java implementation on OpenStack

Question

I want to learn java codes how to "show quota details for user" on OpenStack API.

I can implement quota limit :

String zone = ConfigFactory.load().getString("openstackZone");
NovaApi novaApiClient = getNovaApi(userId, projectId);
Optional<? extends QuotaApi> quotaOptional= novaApiClient.getQuotaExtensionForZone(zone);
Quota quota = quotaOptional.get().getByTenant(ProjectBD.findById(projectId).getProjectId());
ConsoleObjectMapper.getMapper().map(quota, showQuotaBean);

but I cant quotas for usage. For example, I get instance (number), security group(number), ram(GB), volume(number) limit etc. But I cant get information of usage by JAVA code.

                 (I can't get) (I can get)
                    Usage        Limit
İnstance              4           10
Security Group        3           20
RAM                512.0 MB      50.0 GB
Volume                5           10

Can you help me?

Thanks.