The Java Tutorials - Lesson - Regular Expressions
- A lesson explains how to use the java.util.regex API for pattern matching with regular expressions. Although the syntax accepted by this package is similar to the Perl programming language, knowledge of Perl is not a prerequisite. This lesson starts with
- http://java.sun.com/docs/books/tutorial/essential/regex/

gnu.regexp
- Pure Java implementation of a traditional (non-POSIX) NFA regular expression engine. Its syntax can emulate many popular development tools, including awk, sed, emacs, perl and grep. [Open Source, LGPL]
- http://nlp.stanford.edu/nlp/javadoc/gnu-regexp-docs/index.html

Jakarta ORO
- A set of text-processing classes that provide Perl5 compatible regular expressions, AWK-like regular expressions, glob expressions, and utility classes for performing substitutions, splits, and filtering filenames. This library is the open source successo
- http://jakarta.apache.org/oro/

JDK 1.4 Supports Regular Expressions
- Regular expressions are a useful programming tool. The fact that Java now natively supports them simplifies many programming tasks that used to require cumbersome code. A description of the new features on earthweb.com.
- http://www.developer.com/java/article.php/908271

JRegex
- Regular expression support that offers a superset of Perl5.6 regex syntax, compatibility with JDK 1.1). Includes documentation, examples, and demonstration applet. [Open Source, BSD-like]
- http://jregex.sourceforge.net/

jrexx
- A regular expression API for textual pattern matching based on the finite state automaton theory written in Java. It also offers set operations (union, intersection, difference, complement) for combination of automatons. [Open source, LGPL]
- http://www.karneim.com/jrexx/project01/project01.htm

Pat
- A package that provides a mechanism for compiling and matching regular expressions in Java. Download, documentation and news.
- http://www.javaregex.com/

Java Regular Expressions
- Provides a package to perform Regular Expressions in Java. Documentation and download including source.
- http://www.crocodile.org/~sts/Rex/

Jakarta Regexp
- Lightweight regular expressions pattern matcher. [Open Source, BSD-like]
- http://jakarta.apache.org/regexp/

TREX - Tree Regular Expressions for XML
- A language for validating XML documents. Site includes tutorial, specification and sample implementation in Java.
- http://www.thaiopensource.com/trex/

Java Simple Regular Expresions
- Applets reads simple regular expressions and builds a state machine that recognizes regular expression. Provided source code is appropriate for educational purposes.
- http://www.oursland.net/projects/regexp/

dk.brics.automaton
- Finite-state automata and regular expressions for Java. The package contains a DFA/NFA implementation with Unicode alphabet and support for all standard regular expression operations, like concatenation, union, intersection, complement, Kleene star.
- http://www.brics.dk/~amoeller/automaton/