Comment by sxp

Avoiding allocations is the key part: "...we avoid all the garbage". I found the same is true when trying to write high performance Java UI code for Android. If you have to do something complex each frame, make sure to pre allocate or pool your objects. If the hot parts of the code are written in a C-like style, then the JIT and other optimizations can give you C-like performance. You'll still need to write C code if you want vector operations or other processor-specific functionality, but writing in C-like Java can give you C performance while still letting you interact with Java libraries & APIs.