Returning Vectors, Sequences and Maps from Clojure to Java

Question

I've read the excellent answer to Calling clojure from java which shows the new style of calling Clojure from Java.

But the example given just returns a float. How can I return Clojure Vectors and other Sequence types from Clojure to Java? And Maps?

Specifically in this gen-class :

(ns dummy-app.core
  (:gen-class
   :name com.example.dummy
   :methods [#^{:static true} [f [int] int]
             #^{:static true} [getVect [] XXXX]
             #^{:static true} [getMap [] YYYY]
             #^{:static true} [getSeq [] ZZZZ]
             ] ))

what should I put for XXXX, YYYY and ZZZZ? And what types should they be in my Java program?

Update : in response to Tomo's promising answer, if I try to just use IPersistentVector in the gen-clas I get

Caused by: java.lang.ClassNotFoundException: java.lang.IPersistentVector

when I try to create the Uberjar. I assume there's something else I need to do to import these types?

Update 2 : OK, thanks to more comments from Tomo this seems to work :

(ns dummy-app.core
  (import clojure.lang.IPersistentVector)
  (:gen-class
   :name com.example.dummy
   :methods [#^{:static true} [f [int] int]
             #^{:static true} [getVect [] clojure.lang.IPersistentVector]
             ] ))

score 1 · Accepted Answer · answered Nov 20 '14 at 13:21

1

I'd use appropriate interfaces: IPersistentMap, IPersistentVector, ISeq and so on. Check out the source code (https://github.com/clojure/clojure/tree/master/src/jvm/clojure/lang).

answered Nov 20 '14 at 13:21

Tomo

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Thanks. But still not working for me. I updated the question with the extra details. – interstar Nov 20 '14 at 13:37
Well, I guess you need to import appropriate Java classes, with :import clause on the ns macro, right? – Tomo Nov 20 '14 at 13:39

score 0 · Answer 2 · answered Nov 20 '14 at 13:38

0

You can also just specify the appropriate Java interfaces.

Clojure vectors, list and seqs all implement java.util.List

Clojure maps implement java.util.Map

Functions implement both java.util.concurrent.Callable and java.lang.Runnable

answered Nov 20 '14 at 13:38

DanLebrero

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Returning Vectors, Sequences and Maps from Clojure to Java

2 Answers2