There’s no particular reason why deploying to Azure is different (from Camunda’s perspective) than deploying to any cloud service. So the question about Azure specific deployment documentation isn’t relevent when wondering about running Java code with Camunda on some cloud service.
You basically have 2 main choices.
Build a spring boot application containing your java classes, attaching them to service tasks and then deploy that to Azure. This video explains some of the steps.
Deploy Camunda BPM Run to the Azure and then you can deploy BPMN files via the rest api and using the external task pattern build workers (in java or whatever you like) that are triggered when the process moves forward. This video explains some of the concepts.