Closing due to lack of evidence of a bug in the kata.

You say
if the character is "", which isn't so much a character, but an empty string.

The first test for invalid strings is exactly this, and it expects false, not true.

So, I don't see any issue with the kata here. Can you explain further?

There is a bug when testing using the Java, if the character is "" then it will return false, when I try it in the Intellij IDE it works fine, namely it returns a false value, but when I try to run the program through Codewars it returns the true value