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Comment by riku_iki | Hacker News Reader

Not sure about .NET, but Java doesn't have arenas..

It surely has them since Project Panama, as memory segments.

It’s this simple in .NET

   ArrayPool<T>

will elements of arraypool still be tracked by GC with overhead?

Depends on the T.

.NET has value types, explicit stack allocation, low level unsafe programming C style, and manual memory management as well.

java.lang.foreign.Arena

My understanding is that that arena allows you to allocate memory segments, but you can't do much with it, you can't allocate var or object on it like in C++ for example, so its almost useless.

You certainly can, as they were designed as JNI replacement, with the goal to fully support the C ABI of the host platform.

You can either do the whole boilerplate manually with Panama set of APIs, or write a C header file and let jextract do the work of boilerplate generation.

> You certainly can

I am wondering if there is working code example, or this is just speculation?

https://docs.oracle.com/en/java/javase/21/core/memory-segmen...

That Arena is not integrated into language. You can't do something like:

var myObj = new(my_arena) MyClass();

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