Clojure 1.12 consuming Java streams (interop)

[seancorfield]

From the release notes:

Java APIs increasingly return Streams and are hard to consume because they do not implement interfaces that Clojure already supports, and hard to interop with because Clojure doesn't directly implement Java functional interfaces.

In addition to functional interface support, Clojure now provides these functions to interoperate with streams in an idiomatic manner, all functions behave analogously to their Clojure counterparts:

(stream-seq! stream) => seq
(stream-reduce! f [init-val] stream) => val
(stream-transduce! xf f [init-val] stream) => val
(stream-into! to-coll [xf] stream) => to-coll

All of these operations are terminal stream operations (they consume the stream).

See: CLJ-2775

[seancorfield]

Official docs to link to https://clojure.org/reference/java_interop#streams (identical to what's in the release notes -- so we need examples!).

[seancorfield]

user=> (java.nio.file.Path/of "deps.edn" (into-array String []))
#object[sun.nio.fs.UnixPath 0x366665c5 "deps.edn"]
user=> (java.nio.file.Files/lines *1)
#object[java.util.stream.ReferencePipeline$Head 0x684e651f "java.util.stream.ReferencePipeline$Head@684e651f"]
user=> (stream-into! [] *1)

[seancorfield]

Unconvincing example with future as Supplier 😄

user=> (stream-into! [] (take 5) (java.util.stream.Stream/generate (future 42)))
[42 42 42 42 42]