FREJ means "Fuzzy Regular Expressions for Java".
It is simple library (and command-line grep-like utility) which could help you when you are in need of approximate string matching or substring searching with the help of primitive regular expressions.
What is "approximate" (or "fuzzy") string comparison?
Just imagine that you deal with information (like orders) which is sent to you by many people. When these people mention names of places or persons, they could bring to you problems of two kinds:
For example if you are responsible for checking incoming mail in Washington DC, you may want to find letters addressed to US president. You try to find all which contains words "Barack Obama" on envelope. But you soon discover that sometimes people address this person as "Barack Hussein Obama II" and sometimes like "B. H. Obama" and also "Barak H. Abama" (note typos).
You read google and wikipedia and found that you can compare "Barak" with "Barack" and "Baarck" etc. with the help of "approximate string matching algorithm", also called "fuzzy string matching". But after you use or implement some of algorithms you found that it is not sufficient. You need "approximate" substring search, and ability to specify some complex patterns (for example country could be specified like "Russia" and like "Russian Federation" - but it should not be mixed with "Belarussian Republic" etc.
Later you even find out that you sometimes need some automatic substitutions to be described by patterns themselves (for example if you found that the envelope is signed for one of Barack Obama or John McCain, you would like the correct name to be supposed at once, excluding any typos). You now understand that you need regular expressions.
If you want library which can simultaneously use regular expressions and approximate string matching, you will found that here is TRE. But it is for C++. FREJ project is much simpler and far not as efficient, but it is for Java and if your task does not require millions of comparisions against very complicated patterns per seconds - you may found it useful.
Now I am working on filling this resource with descriptions, documentations and also on slight improvement of my library. Simple guide to regexp syntax is already provided and aided with examples (but would be improved further). Also there is working library, javadocs and sample "grep-like" utility (which tests input lines against specified pattern and provides replacement if specified, and if line does match the pattern.