regex - Java: Split string when an uppercase letter is found

Question

I think this is an easy question, but I am not able to find a simple solution (say, less than 10 lines of code :)

I have a String such as "thisIsMyString" and I need to convert it to a String[] {"this", "Is", "My", "String"}.

Please notice the first letter is not uppercase.

Answer 1

You may use a regexp with zero-width positive lookahead - it finds uppercase letters but doesn't include them into delimiter:

String s = "thisIsMyString";
String[] r = s.split("(?=\p{Upper})");

Y(?=X) matches Y followed by X, but doesn't include X into match. So (?=\p{Upper}) matches an empty sequence followed by a uppercase letter, and split uses it as a delimiter.

See javadoc for more info on Java regexp syntax.

EDIT: By the way, it doesn't work with thisIsMyüberString. For non-ASCII uppercase letters you need a Unicode uppercase character class instead of POSIX one:

String[] r = s.split("(?=\p{Lu})");