Guava: CacheBuilder / CacheLoader for compute cache type thing and similar

cachebuilder.clj

;; This stuff is pretty useful in many contexts.

 ...
 (:import (com.google.common.cache CacheBuilder CacheLoader))
 ...
  
  

quantataraxia.core> (with (-> (CacheBuilder/newBuilder)
                              (.weakKeys)
                              (.concurrencyLevel (.availableProcessors (Runtime/getRuntime))) 
                              (.build (proxy [CacheLoader] []
                                        (load [k]
                                          21))))
                      (.put it :answer 42)
                      (dbg-prin1 (.get it :answer))
                      (dbg-prin1 (.get it :something-else))
                      (dbg-prin1 (.get it :blah (fn [] 3.1415))))

(.get it :answer) => 42
(.get it :something-else) => 21
(.get it :blah (fn [] 3.1415)) => 3.1415



;;; 
;;;

quantataraxia.core> (with (-> (CacheBuilder/newBuilder)
                              (.weakKeys)
                              (.concurrencyLevel (.availableProcessors (Runtime/getRuntime))) 
                              (.build #_(proxy [CacheLoader] []
                                        (load [k]
                                          21))))
                      (.put it :answer 42)
                      (dbg-prin1 (.getIfPresent it :answer))
                      (dbg-prin1 (.getIfPresent it :something-else))
                      (dbg-prin1 (.get it :blah (fn [] (println "whot!") 3.1415)))
                      (dbg-prin1 (.get it :blah (fn [] (println "whot!") 3.1415))))
(.getIfPresent it :answer) => 42
(.getIfPresent it :something-else) => nil
whot!
(.get it :blah (fn [] (println whot!) 3.1415)) => 3.1415
(.get it :blah (fn [] (println whot!) 3.1415)) => 3.1415