Jaroslav Tulach is the founder and initial architect of NetBeans, which is not just a well known IDE, but also the first modular desktop application framework written in Java. Maintaining NetBeans Platform, its architecture and APIs has always been the primary focus of Jaroslav. During more than fifteen years of participating in the NetBeans.org project, Jaroslav has seen, made and helped to recover from many design mistakes. Such experience obligated Jaroslav to sit down and summarize in his Practical API Book. The GeekOut tutorial is going to be based on Jaroslav’s recent experience with making NetBeansAPIs better with the help of compile time annotations.