> In fact, of all language runtimes that do generics, the .NET runtime is the only one that specializes. As a C++ programmer I would mention templates as some

> In fact, of all language runtimes that do generics, the .NET runtime is the only one that specializes. As a C++ programmer I would mention templates as something similar. > The problem with specialized generics in the runtime is that they bake the type system of the language into the runtime itself, making the runtime more difficult to work with. When inheritance comes in to play Java ends up storing generic type information in the child classes. It even has to generate bridge methods since Runtime does not really deal with int compareTo( Comparable<? extends T> ) vs. int compareTo ( MyInteger ) . > if you really need performance for this very narrow field of use cases, you're probably not going to be using generic data structures and algorithms anyways An ArrayList<Integer> makes sense in very few cases and is extremely slow, 64 bit pointers to objects that contain useless metadata and a immutable 32 bit int. Sadly an IntList is neither generic nor is it compatible with anything that operates on List<T>s, which results in duplication of a lot of algorithms just to sort primitives. > when I was in college doing a NLP assignment that needed to be fast, my data structures were arrays of doubles because that was the easiest way to reason about and ensure performance. Case in point: In C++ std::vector<double> and the standard algorithm header take care of most of that. If there is some specialized implementation of some algorithm for double values then you can still use that without copy pasting the implementation of everything else.