Not a question, and please don't post solutions in discourse liek that.

I think you might want to go back to Bio 101 ;)

Oh, I thought it was by C#. Thanks @Chrono79.

public static int[] reverse(int n){

That's the initial function's name, he didn't copy the Class part, but as I see it, there is no problem with the function's name. That's java.

I have tried your code, @Zetawarden. To pass the tests, I had to do 2 things.
The first one was to correct function name. The second one was what @Chrono79 has already written. Hope you can solve the kata by the hints.

I don't understand why you wrote it either, return the other array, the one that contains the numbers.
Change this line return new int[j];

Example : n=5 >> [5,4,3,2,1]

You're creating b and then returning a new array?

See the sample tests:

        assertEquals("Congratulations! You're going to have a son.", Kata.chromosomeCheck("XY"));
        assertEquals("Congratulations! You're going to have a daughter.", Kata.chromosomeCheck("XX"));

Are you sure any humanYears greater than 2 should return the same amount of catYears and dogYears?

The assertion error is because the returned value is not the expected one.

expected:<15> but was:<1>

That's because of where you're returning sum (as I've already said ;) ).