Java generics use erasure, and they are backwards-compatible with non-generic-using code. You can still say `var l = new ArrayList();` in the latest Java versions; you’ll get a compiler warning, but the code will compile and run as well as code using `ArrayList<object>` would. C# uses reified generics (which are faster, saner, and more expressive), and standard collections exist in two namespaces (System.Collections vs System.Collections.Generic). If you needed to work with legacy code that uses the non-generic types, System.Collections.Generic.List<T> implements System.Collections.IList (but the code would need to be smart enough to demand the IList interface instead of the concrete System.Collections.ArrayList implementation).
