... and that the verb should in fact be "use" (plural).

Das auf jeden Fall – ein überraschend häufiger Fehler (sowohl im Englischen als auch entsprechend im Deutschen).

No, uses could well be correct, agreeing in number with "one".

Let's make the sentence simpler, and get away from the software jargon.

A. Sally is one of the friends who enjoys black coffee.

B. Sally is one of the friends who enjoy black coffee.

Both are possible. In (A), there are a group of friends at the coffee shop, and most take their coffee with sugar and cream, but Sally is one (maybe the only one) who enjoys it black. In (B), all the friends take their coffee black.

It works either way.

I think I mostly agree with #4.

By using "uses", this "TreeSet" is using "a Red-black tree for storage".

If it had used "use", then the all implementations would use "a Red-black tree for storage".

The coffee example is much nicer without the technical jargon.

But I disagree with #4 on (A). (A) says little or nothing about the other friends.

And so, I have a (C) and (D):

(C) Sally is the only one of the friends who enjoys black coffee. (Sally and only Sally likes black coffee)

or..

(D) Sally is one of the only friends who enjoys black coffee. (Very few enjoy black coffee, but Sally likes black coffee)

Unless she is the only one of the friends who enjoys black coffee.