Writing a Conversational Interface Library - Regular Expressions for I/O

miguelmj profile image MiguelMJ ・3 min read

In the last post we defined the requisites of the project. I started in order and began with the input and output based on regular expressions.

Regular expressions in Java

Regular expressions are supported in Java with the package java.util.regex. Its usage is pretty straightforward for the pattern matching, but does not support string generation.

As usual, someone had already asked what I needed to know in stackoverflow, and thus I found the library Generex, a Java library for generating String from a regular expression.

Setting up the project

Almost always I prefer to work from the terminal. I strongly believe that being able to manage your code without an IDE gives you better understanding of the underlying processes of compiling and debugging. Still, I am not going to refuse the facility of an IDE if what I care about is that the project moves forward.

  • At first, I tried to build Generex from source, but I'm not familiar with this process in Java and it looked like more effort than it was worth, so I decided to go with Maven.
  • I tried to use Maven from the command line. I read some tutorials and got a Hello World compiled, but again I had problems using the dependencies for the real project.
  • What I had to do was clear; I didn't switch from C++ to Java to complicate my life, so I launched Eclipse, imported the Maven project(1)(2) and had Generex up and running in seconds.

A custom Pattern class

Once with my work environment ready, I created a Pattern class. Initially I debated whether it was necessary to make a unified class for the input and output patterns, instead of a separate one for each, but I came to the conclusion that for now I needed simplicity and in the end there was not a big conceptual difference.
This class contained a java.util.regex.Pattern for the matching and a Generex for the generation. I was worried I was using more memory than necesary ,given that I won't be using them at the same time, but again, I followed this quote whose author I never remember:

Is easier to optimize clean code than to clean optimized code.


I have not used JUnit before, so I was glad to discover it's not a big deal. I prepared a single test to check that a simple Pattern could generate different strings, and match them all as true.
The regular expression used for the test is:

(Hi|Hello), how are you( today)?\?

and everything went well, as the output shows ([OK] means that the pattern matched the generated string).

Generated: Hi, how are you today?[OK]
Generated: Hello, how are you?[OK]
Generated: Hi, how are you today?[OK]
Generated: Hello, how are you?[OK]
Generated: Hi, how are you?[OK]
Generated: Hi, how are you today?[OK]
Generated: Hello, how are you today?[OK]
Generated: Hi, how are you today?[OK]
Generated: Hello, how are you?[OK]
Generated: Hello, how are you?[OK]


This was still the easy part and I didn't really expect the test to fail, but this kind of motivation is important, even in the beginning.

I decided to name this project JTASCHE, to make the difference with TASCHE. The code is available on GitHub.

GitHub logo MiguelMJ / JTASCHE

Java Text Adventure and Simple Chatbot Engine


Text Adventure and Simple CHatbot Engine

documentation GitHub repo size


JTASCHE is a java tool for specifying text-based applications that seeks flexibility in the input recognition and response generation.

Currently under development: last commit

JTASCHE is the Java version of TASCHE.

Posted on by:

miguelmj profile



I'm a Computer Science student and programming is my passion. I love learning as much as I love teaching, sharing knowledge is a high human value!


Editor guide