Your solution is wrong and fails with inputs like 8675309 it returns true instead of false.

8675309 ==> [8, 6*, 7, 5*, 3, 0*, 9] ==> [8, 12, 7, 10, 3, 0, 9] ==> [8, 3, 7, 1, 3, 0, 9]
[8, 3, 7, 1, 3, 0, 9] ==> [8, 3, 7, 1, 3, 0, 9] = 31
31 (modulus) 10 ==> 1 , which is not equal to 0, so this is not a valid credit card number

Not a kata issue.

If a resulting number is greater than 9, replace it with the sum of its own digits (which is the same as subtracting 9 from it)

You're not doing that right.

Everything is working on my end, and I am passing the test. But when I attempt, it is saying expected true to equal false and vice versa if I change.

Scala translation

Good problem!

Java:

• Missing fixed tests.
• Random tests are so wide-spread and few that one can get lucky: https://www.codewars.com/kata/reviews/646f983d60b6ad00016a3196/groups/6470d5ce32bedc0001e67dae
• Description states that all elements in array are unique. Random tests do not guarantee this.
• Overall I am not really sure if Java fits the original intent of this kata as you cannot "be concise" with arrays in Java and have to write as much code as with a normal loop so the kata degrades to codegolf the Java boilerplate.

Which language am I missing?

Description doesn't take into account each language-specific character limit.

I updated the description to reflect each language character limit in my CoffeeScript update

But no telling if anyone will ever aprove it

Your refactored solution did not contain what I was looking for. Keep researching :)

Why?! It is not specified in the description - stating this is only a code golf kata, that should be more interesting in the end than its current state.

horrid question