[throwaway03452]

> you will never see `IntStream` kind of workarounds in C#.

You may not see that in Java in the future either. Java will have value objects from the Valhalla project, and part of the plan is to replace Integer with a value object. Then there will be less of a reason to use raw int primitives, because the JVM can treat value objects much more efficiently than normal objects.

[neonsunset]

The difference is that C# has been designed with proper generics since version 2 (pushed by F# research group with Don Syme) and is now on version 13. At the same time, structs have been present since version 1.

All APIs and collection types build on this foundation, with standard library leveraging generic monomorhpization for zero-cost abstractions. Code that would have needed C++ implementation in the past is naturally expressed in pure C#. Generics are fully integrated into the type system at IL level, avoiding special-cased types or bespoke compiler handling (besides monomorphization).

This enables numerous zero-cost features: tuples (unnamed/named), structs with controlled mutability and record structs, pattern matching, stack buffers that do not rely on escape analysis, structs with byref pointers for slice types (Span<T> and friends) which a good two thirds of the standard library accepts. Numeric and vector primitives are used in a simple way without setup requirements like Panama Vectors.

While project Valhalla will get Java's foot in the door in some domains, it will remain a less optimal choice than C#, C++, Rust, etc. Java's evolution primarily serves its ecosystem's needs, whereas C# benefits from being a newer language that learned from both Java and C++ and got influenced by F# and other research projects inside MS. This makes C# more idiomatic and terse. The historical drawbacks - platform lock-in, being closed-source, and having relatively weak compiler - have been resolved over the past ~9 years.