Well to save you from the confusion of all the different tools out there, let me explain:
-For now since you are a beginner, learning Java syntax, core classes, and command line stuff is very important and should be your first priority. Unlike both earlier replies, do not
jump straight into graphics. Make basic command line games using ASCII art. Make almost any game you can think of for the command line. Eclipse is a very useful and powerful tool and as much as you may like it too, I also recommend you to start with the command line. Write an entire command line app using just notepad, compile it, and run it. Start using packages and experience the pain and confusion of compiling and running programs that are in packages.
-When you feel you know and understand Java well enough, jump into graphics using Java2D. Java2D is the java.awt packages and subpackages. These allow you to do custom drawing and offer very, very powerful tools for making 2D graphical apps and games. Also you may learn Swing, Java's GUI widget toolkit. It offers nice tools for making GUIs (Graphical User Interface).
-While you are becoming proficient with Java2D, you will learn and accept one grave and heart-breaking truth: Java2D is slow and unsuitable for professional and graphically expensive games. However, despite this shortcoming, it is the perfect playground for gaming beginners. I advise you to not advance until you have learned basic game systems, designs, code architectural organization, etc...
-Finally, when you notice you are ready for hard-core, speed-hungry games, you may jump into the OpenGL bandwagon. OpenGL is a portable high-level API to interface with graphics cards. It is portable in the sense that it works on almost all graphics cards and all systems, and high level since it abstracts away the differences in graphics card functions and drivers. This means you get to skip the slowness of Java2D and be able to directly access the power and performance of raw graphics card awesomeness. This may all seem neat and amazing but there is 1 drawback......its API is written in C (another language). This means you can't really access it directly from Java without writing native code doing a lot of complicated stuff. Well fear not, a bunch of really cool people wrote a library that lets you access these functions and more, and these cool people named it the Lightweight Java Game Library (LWJGL). As gouessej mentioned, another group of cool people wrote a similar library and called it JOGL. They are both almost exactly the same and the only difference is in your perception of it and your choice. However, it seems the LWJGL community is far bigger than the JOGL community and there is a lot more support for it.
-Slick2D, also mentioned above, is an open-source library whose API looks very similar to Java2D yet uses LWJGL underneath. So it lets you make 2D games using the same API you will soon learn and love without worrying about the details underneath. However, as also mentioned, it is best if you understand the underlying inner workings so you can gain experience and be able to understand any problems you run into.
-There are some libraries that try to simplify your life when making 2D/3D games and GUIs using OpenGL. Such tools include:
-libGDX: open-source library that easily allows you to make OpenGL applications on PCs and Android
-Java Monkey Engine (JME): fully featured Java 3D engine built on LWJGL that has tons of tools for making professional-looking games
-jPCT: Another 3D engine built on LWJGL that to some is simpler and easier than JME yet isn't as powerful.
-Ardor3D: A recently emerging 3D engine also built on LWJGL that looks very promising, from what I've heard it combines the ease of jPCT and the power of JME.
-Themable Widget Toolkit (TWL): A GUI widget toolkit. It is very powerful and allows for full customization of your widgets. This is the "Swing" version of OpenGL
These tools and engines are nice to use if you don't want to get too much into the details of OpenGL. However, it is better if you do because it is just nicer to understand what is going on behind the scenes and will help you debug any problems you run into. These libraries just ease the lives of those who already understand OpenGL, rather than helping ignorant impatient programmers who want to get their hands dirty in 3D designing.
Well this was a long post, and I hope you now understand the current situation of Java gaming and have a basic timeline of your future
If you need any help or assistance, we are always here to guide
you along the way, not to spoon feed you with code. Remember, we're all a bunch of chill dudes sacrificing our time to help newbies because we enjoy it
You can also join us at the #lwjgl channel on the Freenode IRC network
for more help, but know that if no one responds, do idle since we are all on different timezones (half of them live in Europe!).
Good luck!!!! LINKS
-Ultimate Java tutorials: http://tinyurl.com/cqp4as
-Java Resource: http://www.java-gaming.org/index.php?action=resources
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