Problems with the JVM

submited by

Style Pass

2024-10-18 18:30:13

Well, my last few articles might make you think I'm all rosy on the JVM. It's got all sorts of investment in performance, cross-platform compatibility, and backwards compatibility. It has industry adoption and a giant ecosystem of libraries and tooling. But there's still stuff that was just a mistake.

Null pointers are completely unnecessary. They muddy up the whole mess. You have to do null checks before method calls. Their inventor calls them "My Billion Dollar Mistake". Who hasn't been bitten by a NullPointerException?

Java has null pointers. And so does the JVM. Clojure would be a better language without null pointers (in my opinion), but being on the JVM, you're going to get one sooner or later. So Clojure has made nil a common, first-class value. That means you deal with it all the time. I think I use nil way more in Clojure than I ever did in Java. And it's less dangerous, since Clojure uses extensive nil punning.

For instance, in Clojure nil has a type (which is nil), while Java's null has a weird type without a name. nil is a seq and an empty associative collection. It's not perfect, but nils aren't as big of a problem as nulls are in Java.