[kelnos]

If you want those, you can use Vavr[0].

Ultimately the issue isn't the presence or absence of those classes (because they aren't hard to write minimal versions of as a one-off if you need them and can't allow the dependency), it's the pervasiveness of use (or lack thereof) by libraries and especially the standard library.

If Try and Either were added to the Java stdlib tomorrow, the rest of the stdlib would still be stuck throwing exceptions for error propagation, because they can't change the return types of existing methods. The only benefit would be that third-party libraries could feel comfortable enough to use them in their type signatures. But, in practice, most libraries still target Java 8, so I wouldn't hold my breath for that, either.

[0] https://vavr.io