This tool is used to count how many lines of code in your project : ). You can also specify the language type by options. For example the options "Java", "C#" are corresponding to the file extentison ".java", ".cs".
What you need is a system with JDK(Details on click) installed.
There is no third-party dependency in this project, so you can build this project with just one command line:
javac CodeCounter.java
Just input java CodeCounter
to your terminal window(or command line window), and it will tell you how to use this program.