future - Clojure

Code

;; future.clj

(future
  (println "This runs in background")
  (Thread/sleep 1000)
  (println "Done after 1 second"))

(let [f (future
          (Thread/sleep 2000)
          "Result")]
  (println "Immediate return")  ; Prints immediately
  (println @f)) ; Blocks here for 2 seconds if needed

;;;;;;;;;;;;;

(def my-future (future (+ 1 2 3)))

;; Block until result is ready
(println @my-future)  ; Prints: 6

;; Or with timeout (returns nil if not ready in 1000ms)
(deref my-future 1000 :timeout)

;;;;;;;;;;;;;

(do
  (def my-future-3 (future (Thread/sleep 2000) (+ 1 2 3)))

  ;; Or with timeout (returns nil if not ready in 1000ms)
  (deref my-future-3 100 :timeout))

;;;;;;;;;;;;;

(do
  (def my-future-4 (future (Thread/sleep 20) (+ 1 2 3)))

  ;; Or with timeout (returns nil if not ready in 1000ms)
  (deref my-future-4 100 :timeout))