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This code snippet is initializing the Realm SDK in your android application. This is not defining any database yet. You can further set up the app configuration using API.
There is mostly 1 database per Realm Application on the cloud and multiple public/private realms as part of that and is segregated based on the partition strategy you define. You can have multiple databases but they are tricky to use when you have partition sync, as your partition key should be the same in all the databases.
Could you clarify more what you are trying to do and where you are stuck? Are you using Sync or only the local database? If you are using sync, do you have development mode on?
I look forward to your response.