- That's why people like me exist... to help people like you.!
If you want to learn how to create mods for Minecraft, and it requires the use of Java, then just learn Java first.
Java, as a language, is a more basic version of C++, it works totally differently but the syntax is based on C++ only it can't do anywhere near as much. (Sure, some projects come close but they're coded by experts with decades of experience working around Java's limitations).
By the time you know Java thoroughly 5 to 10 years will have past and computers will be almost 1,000 times as powerful as they are today so it won't matter as much.
- Scroll down to Trails Covering the Basics as Generics are probably beyond your reach atm.
- Read the following articles, and check off everything in the table of contents
Getting Started — An introduction to Java technology and lessons on installing Java development software and using it to create a simple program.
Learning the Java Language — Lessons describing the essential concepts and features of the Java Programming Language.
Essential Java Classes — Lessons on exceptions, basic input/output, concurrency, regular expressions, and the platform environment.
Collections — Lessons on using and extending the Java Collections Framework.
Collections might cover, or at least mention, Generics a little but by the time you get to it you'll be more prepared for it.
Some of the best programmers in the world started when they were only 12 to 12 years old, and having Minecraft as a motivator really does give younger programmers something to reach for with more instantaneous visual (3D to boot) feedback of their work.