Perhaps because of the title, many/most of the comments here are off-topic. I was hoping to see more discussion about algebraic data types, strengths and weaknesses of the Java implementation, technical comparisons to other languages, etc.
All the existing Java code doesn't go away, so is it really going to be nicer to have code like this mixed randomly into that?
How about intersection and union types? (NO, sealed classes are not a substitute for unions).
But, yeah, in my view JDK 21 is a a disappointment. I rarely want pattern matching, but I would like properties please and records are nice, but actual tuples are more useful. Etc.
As long as the object signature matches the interface as parameter then you can use it.
1. https://github.com/manifold-systems/manifold/tree/master/man...
I have some use cases in mind and think it will be very helpful. I have been converting a 10+ year-old code base to modern, functional-style Java and believe that sealed types and pattern matching will help us further simplify our code and eliminate more usages of nullable values.
A challenge for us will be that we need the core library to stay on JDK 8 for a while. But, in general, I am finding that you can implement a JDK 8 library that works well with newer JDKs if you are careful (and willing to write more verbose code using the older syntax/libraries to support the newer paradigms)