In 2009 the authors developed an open source Java application and framework, GraphsJ, to help the students in their approach to the study of graph algorithms, by guiding them to understand their logical structures through experiments on numerical instances. After four years, the availability of Java 7 and of new tools suggested the implementation of a new major release. We present a new major release, GraphsJ 3, whose implementation in Java 7 maintains the main characteristics of a useful educational application: Portability, extensibility, ease of use and availability as open source software. The new release provides a redesigned architecture, implemented through cutting-edge languages and technologies and a robust Maven-based build. The presented Java framework constitutes a further step towards the implementation of didactic instruments for the teaching of graph theory. Future developments will include extensions to ease the automatic addition of new algorithms.