For about a year now – so called lambda expressions can be used by Java developers. But what does it mean... Lambda? The talk will be about story behind, from a little bit more scientific point of view. Church Lambda calculus, Entscheidungsproblem and incompleteness theorem. However, almost all of that will be presented in Java. There are going to be shown some very crazy code pieces such as infinite lazy lists and perfectly unusable implementation of Boolean (based on Lambda expressions).