CSC/ECE 517 Summer 2008/wiki1 1 mf

Regular expressions in Ruby versus Java

Ruby supports regular expressions as a language feature without the inclusion of any special classes or modules. Java on the other hand does native regular expression support and it requires the use of special regular expression packages to use them.

Ruby regexp support in more depth

Since Ruby borrows it syntax from Perl the is nothing more than the simple syntax of:

/pattern/modifiers

Java regexp support in more depth

Support for regexp

Java has been around for a while have has never had native regexp support. Because of this regular expression packages had to be created. There was no comprehensive support for regexp support from Java's main contributor, Sun, until Java 4. Because of this there are multiple 3rd party regexp packages for Java floating around:

• java.util.regex The most widely used for regular expressions now due to its inclusion in the JDK since Java 4. This document will assume from this point forward that we are using this package for our regular expressions in Java.
• Jakarta Around since 1996, Jakarta was donated to the Apache Software Foundation and is under an open-source, BSD style license
• dk.brics.automaton Automaton is known for being the fastest of the Java regexp implementations
• And the list goes on...

Classes with regular expression abilities

String class

The String class provides simple regular expression support. It is the quickest way to write code to do matching or replacement. However, it is not very fast and therefore should not be used if performance is a factor.

Pattern class

The Pattern class

Matcher class

The Matcher class

References

• Ruby Regexp Class - Regular Expressions in Ruby
• Using Regular Expressions in Java
• java.util.regex
• Jakarta
• dk.brics.automaton

-- Michael Frisch (Tuesday, June 3, 2008)