This stuff doesn’t get written because people are stupid. It solves real problems people have, and it’s the easiest way to solve them in a language that’s fundamentally inadequate. When people think HKT or monads or what-have-you aren’t necessary in a language, I point them at Spring for the examples of what happens when a language doesn’t have them.

For the lack of a nail,
    throw new HorseshoeNailNotFoundException("no nails!");

For the lack of a horseshoe,
    EquestrianDoctor.getLocalInstance().getHorseDispatcher().shoot();

For the lack of a horse,
    RidersGuild.getRiderNotificationSubscriberList().getBroadcaster().run(
      new BroadcastMessage(StableFactory.getNullHorseInstance()));

etc.

I particularly like QualifierAnnotationAutowireCandidateResolver and SimpleBeanFactoryAwareAspectInstanceFactory as well

Mamas (and papas) don’t let your babies grow up to be Java developers….