Recent proposals for adding parameterised types to Java have left a number of important practical issues undiscussed. In this paper we present the language Genja which is a new generic extension of Java oriented towards practical support for generic collection types. We discuss design alternatives related to extending the power of unconstrained genericity, solving the weaknesses of constrained genericity in other proposals and defining the compatibility of named and anonymous instantiations. By enhancing support for reusability and providing a higher level style of programming via a library of standard generic collection types Genja aims to extend Java's contribution to efficient software production.