Immutability is a property I look after when designing most of my classes. Achieving immutability requires: A constructor initializing all attributesNo setter for those attributes However, this design prevents or makes testing more complex. In order to allow (or ease) testing, a public no-arg constructor is needed. Other use-cases requiring usage of a no-arg constructor include: De-serialization of serialized objectsSub-classing with no constructor invocation of parent classesetc.