Java strings enjoy heavy optimizations, including SSE4.2 and AVX intrinsics. Implementing your own byte[] wrappers (which Strings are) might be useful however i

Java strings enjoy heavy optimizations, including SSE4.2 and AVX intrinsics. Implementing your own byte[] wrappers (which Strings are) might be useful however it won't replace the built-in Strings. In short: a general purpose String substitute in Java would be an extremely poor idea.