numbers[i] = -numbers[i]; modifies the input array, which is considered "hidden side effect" and should be avoided.
Also, especially in Codewars, modifying the input can confuse the testing code and mark your code as incorrect, so be careful.

• Use the search bar to search for "binary" - https://www.codewars.com/kata/search/my-languages?q=binary
• Use the tag search to search - https://www.codewars.com/kata/search/my-languages?tags=Binary

To create a Kata:

• Hover over your avatar in top right hand corner and click "New Kata" - https://www.codewars.com/kata/new
• Use the "Help" button to get help with design and authoring. Make sure your Kata is unique by searching your idea using several terms in the search bar. Also look at testcases in documentation and other Katas for an idea of how to make one.

Post under codevortex comment down below, so that the Java author can be notified :)