JITs don't improve a hashtables performance as they are dominated by memory access patterns (eg, open vs closed addressing), load factor, and hash quality. Of

JITs don't improve a hashtables performance as they are dominated by memory access patterns (eg, open vs closed addressing), load factor, and hash quality. Of those 3 factors, the first is borderline impossible to optimize in Java at all. Regardless, the runtime isn't helping with any of those 3, it requires changes to the algorithms used. Which doesn't seem to be happening in Java land broadly? It's possible that the JVM just ignores its c++ code, sure, but that's not commentary on Java or the Java ecosystem. Also offline compiler optimization has so far consistently outpaced (or at least kept up with) JIT optimizations. So it's incorrect to consider the native code as static anyway unless you're just never upgrading the compiler.