This doesn't handle null check . what is str is null ? your code throws NullPointerException

It's for case insensitive, so you don't need to declare the upper case or lower case on the pattern.

zeta zeta zeta

What does that (?i) do?

（?i）is nice.

I wrote 10 separate replace statements lmao

I always forget that you can do this in one return statement and end up creating a new string first. Bravo!

Titsnium, yeah, it's so easy but mind-blowing.

Jesus Christ, well ya learn something new everyday, I just learned you could do this.

Bruh I spent hours tryna use a flippen bubble sort -ish to go through every letter to check if its a vowel, and I could've just done this?? Thank you

This is sick, had no idea you could just replace like that :)

I didn't know you could replace multiple letters at a time so I wrote a new replaceAll for each letter; this is much simpler. Good job

dh! yr sltn n't p t th mrk, mn srsly, wtf s tht??

"Signature will always contain 3 numbers;" so it can't be null.
when s.length == 5, Arrays.copyOf(s, 2) will truncate the array and returning an array of length 2.

Very nice... I was just forgetting the RE (plus a bit of stream know how)

Case insensitivity