New languages bring new ways of thinking and teach us new principles and tools that we can bring back to your day to day language. Using a real application as an example, we will learn how to build and design Java applications that follow Clojure’s functional principles using just core Java, without any libraries, lambdas, streams or weird syntax; and we will see what benefits those functional principles can bring. No Clojure or functional programming knowledge required, just plain old good Java.