Is Clojure / Java interop slow?

Question

Is calling Java from Clojure slow in comparison to pure Clojure code? And is this because there is always reflection under the hood? Thanks.

Answer 1

Not really. You can generally write java interop code in clojure that is exactly as fast as equivalent java code, including type hints to eliminate reflection. Generally that means its more low level, much more verbose and faster than idiomatic clojure.