You said you watched the material. But have you perform an activity on the material? Whether it is homework exercises that test your conceptual and fundamental understanding of Java.
You do not learn Java just by watching someone. Sure you might understand the concepts but you need to test your understanding by yourself. You really need to think about this stuff and apply it right away to go from a passive mind to an active mind. Start thinking of the algorithm on paper, implement on paper and make sure you understand what problems can potentially happen. If there is no problems on paper, implement the code on the IDE.
What new material is troubling you? Do you understand the entirety of the concepts you mentioned earlier?
Since you are still learning the basics of the language, you should not even start programming 3D games yet alone 2D games. It is not how programming works. I really think you need to actively do the exercises to really hone your skills as a programmer.
You need to have at least met these minimum requirements: an intermediate level understanding of the programming language(the short answer is doing the exercises in a Java textbook you cannot go wrong with an academic textbook), on top of general knowledge of graphics that is built into Java. Good coding style is a must. Even a simple game requires a huge codebase.
You can easily download an open source project of a 2D game and see which areas you still need to know and improve on. This could be libraries you never worked with or just conceptual knowledge you have missed out on.
Eventually, you will explore the "object-oriented" side of things and it is super important because after all Java is an object-oriented language.
Tip: Always have the Java API as a handy reference. That way you can look up which method correspond to which class. An example suppose you forgot where the parseInt method is, google will tell you it is from the Integer class.
Tip: Never mix Awt and Swing libraries together. They are not meant to be mixed because they are different libraries.
Source: I programmed several 2D Java games.
Edited by warnexus, 10 September 2013 - 09:32 AM.