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Comment by noctune | Hacker News Reader

>High-performance Java is indeed basically writing C in Java, including using you own byte array for memory.

Oh, I wish. For example, in C you can easily return multiple values through pointers. In Java, you have no such luxury without allocating so it's even less flexible if you can't allocate.

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I’m not sure what you have in mind but returning pointer to a value on the stack may very well be a huge error.

I think they meant you allocate data once and pass their pointers to a function to put its outputs there. `void return_multi(T* out0, M*out1);`

But then you can just pass in a mutable object as well in java.

Of course it's a huge error, which is why you should never do that. Instead, you pass the addresses of local stack variables to that function as pointer arguments and let that function write its outputs there. Voilà, multiple return values without heap allocations.

Or you pass `this` and set a field of that in a function, which is equivalent.

That's a bit of a stretch using the word 'return' there. Forgive my exactness, but return implies, well, returning a value from a function.

I'd say that Java has similar semantics to C. One can easily pass object references to a function that sets their data. That looks and behaves almost exactly like C. The fact that the references are allocated on the heap is an implementation detail.

Let me be clear, a pointer to a struct on the stack in C is obviously not the same as a reference to an object allocated on the heap in Java. The point is that from the point of view of what the language induces you to do, Java and C are similar. Anyone that has used older libraries in Java can attest to this; they look and feel remarkably like C.

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