Cool

Wow. It's cool

Nothing. Regular string concatenation faster that String#format. You can find in google performance of regular concatenation and String#format.

In case when sum of all numbers < k your code will be execute infinity

bad performance

Yes, it short solution, but performance of String#format is very bad.

I'm sorry.
Thank you.

O.o

Short but not effective

Yes, your solution is shorter. But I think that we (developers) should write faster code. Imagine that your method will execute 1_000_000 times in production every 1 minute. It will be slow.

Also I think that this kata we can't solve with regex, because we have several replace templates.

Sorry for bad English.

This will create 5 new String instances. Also this solution will make 5 loops for replace all characters.

Bad. Very low performance. You call #generateMap twice in #variance. Also you sum Double wrapper objects. It call many box and unbox operation, this operations is slow.

And this can throw NPE if we pass null as name or null as password