This situation is becoming more common as the Java platform evolves, notably with the addition of collection classes to JDK 1.2. Other languages provide additional supportfor this situation: in C++, it is supported with templates; in Ada, it is supported withgenerics; and in ML and Haskell, it is supported with parametric polymorphism. This note proposes GJ, an extension to the Java programming language that sup- ports types with parameters. GJ programs look much like the equivalent Java programs,except they have more type information and fewer casts. The semantics of GJ is givenby a translation into the Java programming language. The translation erases type pa-rameters, replaces type variables by their bounding type (typically Object), adds casts,and inserts bridge methods so that overriding works properly. The resulting programis pretty much what you would write if generics weren’t available. The translation isdesigned so that new GJ code will work with existing Java libraries, even when thelibraries are available only in binary class file form.