String.split with ** crashes

Question

I come across a very strange problem when doing a split on a String. The second line of the code below crashes:

String[] parts1 = "2 xy 3".split("xy"); //OK!
String[] parts2 = "2 ** 3".split("**"); //CRASHES java.util.regex.PatternSyntaxException: Syntax error in regexp pattern near index 1: **

Answer 1

Try this:

String[] parts2 = "2 ** 3".split("\\*\\*");

The problem is that the * has a special meaning in regex patterns, so the workaround is to use double-slash(since single slash would demand an escape character) before a *

For more info on how regex works in java, probably my slide on SlideShare would be useful.