Edit: Aparapi has been open sourced and many issues have already been fixed and improved.
If you have an AMD GPU/APU, you should try Aparapi. This software lets you write OpenCL-code in Java pretty high-level. The idea is that is sort of that it processes the Java intermediate code to search for loops and then create optimised OpenCL-kernels. Just download Aparapi and try the two examples. As the current version is still in alpha, it is not flawless yet. What I think is important when having worked with Aparapi is that you learn how to keep it simple – like you know that you can gain most speed on straight roads and turns slow down.
The Aparapi-team tries to avoid explicit defining of local memory, but it is still possible by using the @Local annotation. Such decisions show the team wants Aparapi to be high-level. It also integrates well with JavaCL and JOCL, so for the kernels you already have created, you can mix. You can also check out a video introducing Aprapi (it is video 15, if #-linking doesn’t work).
Time to create your own project. As not all errors are documented or are solved in the upcoming version, below you will find a list of common errors and how to easily solve them.