It's a good style in Java to keep classes immutable if possible. This prevents accidential changes and makes them thread safe by design.

The "Options" classes like "DeleteStreamOptions" are currently mutable, which is kind of unexpected. It looks like a builder, but mutates the content of the instance:

DeleteStreamOptions opts = DeleteStreamOptions.get(); // Defaultopts.softDelete(); // Now softopts.hardDelete(); // Now hard

I would suggest to create a real builder that returns an immutable instance.

Here is a short example of how the builder pattern would look like:
https://github.com/EventStore/EventStoreDB-Client-Java/compare/trunk...michael-schnell:issue-148?diff=split

If you think this is a good idea, I can create a pull request to discuss this further in detail in the PR.