Currently MongoClientURI can be created either from String or String + MongoClientOptions.Builder and can't be created from existing MongoClientURI with some alterations.

I propose adding a builder (public static inner class in MongoClientURI would be OK, I think) with convenience static methods like MongoClientURI.builder() and MongoClientURI.builder(MongoClientURI from).

Builder itself would have convenient methods like hosts(String...), hosts(List<String>), database(String), collection(String), username(String), password(char[]) and a number of methods for standard options, present in ConnectionString/MongoClientURI.

If this proposal is acceptable, I'll publish prototype on github.