Munich Clojure Workshop - 04 - Java Interop

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Java Interoperability Friday, October 11, 13

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Access Java in Clojure Friday, October 11, 13

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Calling Methods Friday, October 11, 13

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(.method object) Friday, October 11, 13

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(.toUpperCase "abc") ;; => "ABC" Friday, October 11, 13

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(.method object x y) Friday, October 11, 13

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(.equals "a" "b") ;; => false Friday, October 11, 13

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(.getName String) ;; => "java.lang.String" Friday, October 11, 13

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(Class/static-var) (Class/method) (Class/method x) (Class/method x y) Friday, October 11, 13

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(Math/PI) ;; => 3.141592653589793 (Thread/activeCount) Friday, October 11, 13

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(.println (System/out) "hello") Friday, October 11, 13

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(.toUpperCase "abc") (. "abc" toUpperCase) Friday, October 11, 13

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(Thread/activeCount) (. Thread activeCount) Friday, October 11, 13

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(.equals "a" "b") (. "a" equals "b") Friday, October 11, 13

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(.println (System/out) "hello") (. (. System out) println "hello") (.. System out (println "hello")) Friday, October 11, 13

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(.. Runtime getRuntime availableProcessors) Friday, October 11, 13

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New Objects Friday, October 11, 13

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(new Object) (Object.) (java.util.HashMap.) (Integer. 5) Friday, October 11, 13

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(let [hashmap (java.util.HashMap.)] (.put hashmap "a" "b") (.get hashmap "a")) Friday, October 11, 13

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(import [java.util HashMap ArrayList]) (HashMap.) (ArrayList.) Friday, October 11, 13

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(let [hashmap (HashMap.)] (.put hashmap "a" "b") (.put hashmap "x" "y") hashmap) Friday, October 11, 13

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(let [hashmap (HashMap.)] (.put hashmap "a" "b") (.put hashmap "x" "y") hashmap) (doto (HashMap.) (.put "a" "b") (.put "x" "y")) Friday, October 11, 13

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(instance? HashMap (HashMap.)) Friday, October 11, 13

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Implementing Interfaces Friday, October 11, 13

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(.start (Thread. target)) Friday, October 11, 13

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(reify Interface (method [this x y z] body)) Friday, October 11, 13

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(reify InterfaceA (method-a [this x y z] body) InterfaceB (method-b [this m n] body)) Friday, October 11, 13

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(.start (Thread. target)) Friday, October 11, 13

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(let [target (fn [] ...) thread (Thread. target)] (.start thread)) Friday, October 11, 13

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(let [target (reify Runnable (run [this _] (println "hello"))) thread (Thread. target)] (.start thread)) Friday, October 11, 13

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Miscellanea (if time allows) Friday, October 11, 13

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(make-array (Integer/TYPE) 5) (aset (to-array [1 2 3]) 1 5) (into-array [1 2 3]) Friday, October 11, 13

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Access Clojure in Java Friday, October 11, 13

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Creating Class Friday, October 11, 13

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(gen-class :name my.namespace.MyClass) (compile 'my.namespace) (my.namespace.MyClass.) Friday, October 11, 13

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(gen-class :name com.example.Hello :methods [[hello [String] String]]) (defn -hello [arg] (str "Hello, " arg)) (.hello (com.example.Hello.) "Jan") Friday, October 11, 13

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(gen-class :name com.example.Hello :prefix Hello :methods [[hello [String] String]]) (defn Hello-hello [arg] (str "Hello, " arg)) (.hello (com.example.Hello.) "Jan") Friday, October 11, 13

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(gen-class :name com.example.Hello :init init :constructors {[String] []}) (defn -init [arg] (println "Hello, " arg)) (com.example.Hello. "Jan") Friday, October 11, 13

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(import [clojure.lang Seqable]) Friday, October 11, 13

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(gen-class :name com.example.Hello :init init :state state :constructors {[Seqable] []}) (defn -init [seq] [nil seq]) (com.example.Hello. [:a :b :c]) Friday, October 11, 13

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(gen-class :name com.example.Hello :init init :state state :constructors {[Seqable] []}) (defn -init [seq] [nil seq]) (com.example.Hello. [:a :b :c]) (defn -toString [this] (str (.state this))) Friday, October 11, 13

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(gen-class :name com.example.Hello :implements [java.io.Serializable]) Friday, October 11, 13

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(ns org.example.namespace (:gen-class)) (defn -main [arg] (println (.toUpperCase arg))) (compile 'org.example.namespace) java org.example.namespace hello! Friday, October 11, 13