These tutorials are designed to be as clear and concise as possible. They assume that you have at least a basic understanding of Java and Object-Orientated Programming concepts, and will be difficult to follow if you do not.
Java is one of the most widely used programming languages today. As such, there are innumerable resources for learning it. The best option is to take a class at your school or local community college. For American students, the AP Computer Science A course covers Java, general programming practices, as well as many basic OOP concepts. There are also many MOOCs (Massive Open Online Courses) that offer collegiate-level courses for free. The most notable are Coursera, edX, and MIT Open Courseware.
If you would like to contribute to this project, submit new tutorials or just fix typos and errors, you can fork the repository and send me a pull request. This project was deployed on Github Pages for this very reason: community involvement. See: How to Contribute.