That is an interesting read, seems some were having a hard time grasping the benefit of having compiler checks for potential null dereferences. Having worked with null safety in TypeScript and Kotlin the extra bit of strictness is nice.

I remember back in 1995 thinking that it was stupid for Java not to have generics, so instead you had to always cast Vector/Hashtable elements from Object, or implement your own type-specific container classes for every element type (and there wasn’t even a preprocessor to facilitate the latter).

Sum types I didn’t really miss, because you can implement a type-safe equivalent using the Visitor pattern, and retain an interface-implementation separation that native sum types typically don’t provide.

The biggest design issue with adding value types and non nullable to Java, is that the number one design requirement of any solution is not to break Maven Central.

Every compiled JAR out there has to keep working as always on a JVM with updated semantics, and worse code has to be compatible, when passing class instances around between old and new code.

Then there are the guest languages on the JVM as well.