Monday, June 15, 2009

Slashy strings in Groovy

Groovy has done a great job of enhancing Java Strings. It offers a lot of features like String interpolation with GStrings, triple quoted Strings, multi-line Strings, and slashy Strings.

In this post I will talk about slashy Strings in Groovy. But before doing that let us see how we represent a regular expression in Java. Let's say I have a list of fully qualified file names and I want to match all files in my 'c:\tmp' directory.

I would create a String to represent my regex in Java like this:
String exp = "C:\\\\tmp\\\\.*"

The four '\' are needed because '\' is a meta character in regular expressions, so we need to represent a '\' as a '\\'. Because a '\' is used for escaping special characters in Java, we need to represent '\\' as '\\\\'. Wow doesn't this look cumbersome. Well, this is not just one case. Regular expressions make use of the '\' character for special classes. Everytime we want to use a '\w' or a '\d' or something like that we will have to use '\\w' and '\\d' instead.

Slashy Strings in Groovy give us a way around this by allowing us to represent regular expressions just like they would be represented without having to escape the '\' in Java.

Using them we can write

def file = /C:\\tmp\\.*/

Notice that slashy Strings have to be surrounded by forward slashes, and are mostly used when Strings need to represent regular expressions.

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