Dayflower is a photo-realistic realtime renderer written in Java.
The engine primarily uses a rendering technique called Path Tracing, which is in the family of Ray Tracing algorithms. As secondary rendering techniques, Ambient Occlusion, Ray Casting, Ray Marching and Ray Tracing may be used.
The early test implementation of Dayflower, which you now can find on GitHub, uses a library called Aparapi. This library is responsible for decompiling the Java bytecode into OpenCL C99 on the fly. This OpenCL C99 is then compiled into binary code that is executable by your specific GPU.