This talk is a collections / streams deep dive for the functional programmer on the fence between Scala and Java. Among those of us who have picked up Scala, who hasn't — at first at least — been puzzled by an error message regarding the enigmatic `CanBuildFrom` ? And with the arrival of Java 8 and its streams, isn't it time to wonder which approach to adopt when coding with collections ? We'll start with a quick comparison between Scala collections and Java stream, before looking at their internals, showing through compiler errors, performance benchmarks and type wizardry that those are really two tools with different design goals. You should come out of this talk wiser about when to use the Java or the Scala approach, and better equipped to deal with potential compiler errors in the future. This talk is built in a progressive way, and there will be some takeaway for every skill level, both in Java and Scala. Recording me on audio and/or video: YES Bio : François Garillot joined Typesafe in 2011 after a past life in type theory. He worked at the interface between the Scala compiler and interactive requests, such as those made by the Scala IDE. He now works on big data analytics on the JVM, with a keen interest in Spark. Blog : http://blog.garillot.net -- François Garillot