ECOOP 2011 – Object Oriented Programming : 25th European Conference Lancaster Uk July 25 29 2011 Proceedings This book constitutes the refereed proceedings of the 25th European Conference on Object Oriented Programming ECOOP 2011 held in Lancaster UK in July 2011. The 26 revised full papers presented together with three keynote lectures were carefully reviewed and selected from a total of 100 submissions. The papers cover topics such as empirical studies mining understanding recommending modularity modelling and refactoring aliasing and ownership; as well as memory optimizations.