In Java, it would require at least an order of magnitude more code. Additionally, you'd have to know exactly how to do it from the beginning, since it is much more difficult to experiment. High performance computing is not something that is fabulously well documented, so you have to poke around a lot to discover how things work. To see what I'm talking about, you should compare the codebase of neanderhtal (20.000 lines of code) with roughly similar libraries in Java (ND4J is something like 400.000 lines of code), or even Python (numpy is roughly 250.000).