Issue JDK-8280101 requests that String.split should keep the delimiter for grouped regex. This is a non-negligible behaviorally incompatible change and would probably break much existing client code.

A safer alternative is to add API points to both String and Pattern, like
String.splitWithDelimiters(String regex, int limit);
Pattern.splitWithDelimiters(CharSequence input, int limit);

Adding this functionality outside the JDK is somehow more complicated than necessary, so it makes sense to add it in the JDK itself.