This is reasonable -- maybe it's confusing if it's not a good application of streams. I've practicing using stream solutions, (even if there are other ways of doing something) so I was pleased to see this here.

I tend to disagree, this way of doing thing is similar to functional programming.
I woulad have added a map step for the replace call.
ALready said but of course a joining is better than this reduce combined with the get call.
If you absolutely want to a use a reduce, maybe you can use the other version with a initializer
".reduce("", ...)

Superb solution

Can you expand your answer - I would say that solution is comparable to one using for loop

Do you even understand this code? Also: in your solution you've done exactly same thing as author of this soulution (yet less elegantly)

Coding all that at return it´s not best practice.

you used a library, thats cheating?

this way of doing it is very slow. but it has little code. do a runtime comparison with other codes

Not cool dude

This is amazing. I just realized that there are better and greater programmers that really do eat code! You are a code-eater!