This has nothing to do with regexes. The delimiters argument is a set of characters that is used to split on, not a proper String. So in your example, if any |, A, B etc is encountered, that is used to split on. Either that's case insensitive, or your example isn't 100% accurate.
You should check out String.split (or in Java 8, Pattern.splitAsStream). As said, the | is a meta character that you should escape. You can also use Pattern.quote to return a regex that treats the String as a literal value.