java nothing monad option maybe some maybe-monad option-monad java-21

java monads types jvm algebraic-data-types error-handling try jdk adt result either sum-types railway-oriented-programming either-monad result-type maybe-monad try-monad result-monad sealed-class

value optional maybe value-object nullable optionals nullable-type maybe-monad optional-chaining optional-type return-type optional-parameters

java lambda functional-programming tuples io-monad algebraic-data-types monad functor lenses monoid semigroup optics either hlist profunctors traversable coproduct maybe-monad bifunctors try-monad

java monad maybe maybe-monad