1.2 seconds was hello world in clojure, the Java hello world presented the numbers below, so it's mostly clojure that is slow:

$ time java Hello Hello world 0.04user 0.01system 0:00.12elapsed 43%CPU (0avgtext+0avgdata 15436maxresident)k 29672inputs+64outputs (82major+3920minor

While 120ms elapsed is not stellar, it's rarely a problem with how the JVM ecosystem looks.

Please be kind to reread it.

Startup time of a simple Java application and therefore also whole JVM is 0.4s (in the linked article).

1.2s is for the implementation in Closure that includes its additional quite heavy runtime.

I read it fine, but Clojure is an application of the JVM. The fact that a popular interpreted language of the JVM takes 1.2 seconds for hello world is a problem of the JVM itself, or at least it's ecosystem. An interpreted language in C wouldn't take nearly that long.

The way an interpreter is implemented and the language it runs on don't have anything to do with each other.

A Clojure interpreter written in C, if written the same way as for Java, it would run just as slow, given the way it is building Clojure every time the application starts.

That's clojure, not java. JVM startup is much faster.