Default interface implementations are nothing new. In Scala for example, if you create a Map, you can get it to automatically construct a MapImpl, without havin

Default interface implementations are nothing new. In Scala for example, if you create a Map, you can get it to automatically construct a MapImpl, without having to know it. A really common case in many code bases is 1 implementing class, and 1 mock/testing class, and this fits the common case really well. I think "beauty" is really a subjective consideration when it comes to programming languages.