Often in go I’ll create some data structure like a map to hold the new value keyed by the original index (basically a for loop with goroutines inside that close over the index value) - then I just reorder them after waiting for all of them to complete.

Is this basically what Java is doing?

I think that maybe the techniques in this article are a little more complex, allowing you to optimize further (basically continue working as soon as possible instead of just waiting for everything to complete and reordering after the fact) but I’d be curious to know if I’ve missed something.