Sandip's answer will work for the core Processing library (with the caveat that you should use the latest version, not version 2.2.1), but like you've discovered, gicentre doesn't have a maven repository.
You can download the various gicentre libraries from this page. Each of those libraries comes as a .zip
file that contains a .jar
file.
Now that you have the .jar
file, it's just a matter of adding that .jar
to your classpath. How you do that depends on how you've set up your project. The simplest way to do it is to use the command line to compile your project, and then you'd use the -cp
argument. You've said you're using Maven, so Googling "maven local jar" will lead to a ton of results, including this one: How to add local jar files to a Maven project?
But note that you don't have to use Maven. You could just set the classpath yourself, either via the command line or via your IDE settings. For simple projects, this can be a better option, especially if Maven is giving you trouble.