I recently had a similar project [0] and wrote the first version in Java. In some cases it took almost an hour to render a simple 6 bit per color channel image. After that I rewrote it in Go and got it down to ~120s. I think this is mainly due to the fact that the Java version lays way to heavy on OO and does a lot of dynamic memory stuff and the rewritten Go version uses simply 2 (or 3) large arrays.
I think in our case it wasn't a raw performance thing but rather the fact that go's proximity to C made us code smarter (=
That is true, while it often using more memory the same code in Java is usually faster than the same code in Go. The thing is- as you aptly pointed out, the idiomatic Go solution is not the same code and is often lighter and faster.
[0]https://github.com/31415us/olga basically a straight up copy/reimplementation of joco's [1] response to [2] [1]http://joco.name/2014/03/02/all-rgb-colors-in-one-image/ [2]http://codegolf.stackexchange.com/questions/22144/images-wit...