ReplaceAll with Backreferences
Regex functions can give you fast replacements in Java, along with the readability of Perl. Here's an example of using a replaceAll to mask out certain digits in a credit card number.
<geshi lang="java5">
String account = "1234567890123456"; String replacement = account.replaceAll("(\\d{4})(\\d{2})(\\d{6})(\\d{4})", "$1 $2XX XXXX $4"); assertEquals("1234 56XX XXXX 3456", replacement);
</geshi>
Another fun regex can simulate the the unix 'basename' function.
<geshi lang="java5"> assertEquals("RegexTest", this.getClass().getName().replaceAll("(?:\\w+\\.)*(\\w+)", "$1")); </geshi>