One important subject to be analysed on languages is its type system. Having a general overview of a type system can provide us information about syntax performance, optimisations and may help us to understand how statements are evaluated. And those are topics that we shall consider for language evolution and development. This talk will provide a gentle introduction to type theory, how it helps us with IDE's and type inference and how can we apply some of its concepts in Java and other languages build on the top of JVM, such as Scala and Clojure, providing a comparison between the type system of such languages. Topics: * Why Type Theory? * Quick introduction to logic and Lambda Calculus * Where are those concepts used? * An analysis of Java Type System * Clojure Type System * Scala type system Hanneli Tavante (@hannelita) is a developer addicted to code, learn new programming languages, blow capacitors, do some C programming and commit useful (or not) code for random Open Source Projects that she finds at Github. She tries to help the community by writing blog posts and organising meetups about NoSQL, programming languages and Math/Physics/Science. She also likes Math, Lego, dogs, hardware, and [much] coffee. [BRC-3050]