The "native HashTable" referred to here is the string hash table that's inside the JVM. The JVM has to intern strings from class files' string literals here, so it's all implemented in native code. The comment about performance probably refers to Java constantly improving in performance because of improvements to the JIT compiler, whereas that native HashTable in the JVM is pretty static in performance unless somebody rewrites it or if the C++ optimization gets significantly better. Essentially Shipilëv is saying that Java code gets faster more quickly than the C++ code in the JVM.