There's room for two approaches in Java really. The JIT can be smart and use SIMD instructions where it can see they are applicable, but there's also room for a

There's room for two approaches in Java really. The JIT can be smart and use SIMD instructions where it can see they are applicable, but there's also room for a small DSL like API that allows library authors and other very experienced users to express a suitable algorithm and have it easily translated into the SIMD instructions available at runtime. Anybody interested in the latter should take a look at the work being done under project Panama.