It depends on how you define interoperate. The way you phrase this it sounds like the only answer is the JVM. In which case: https://hackage.haskell.org/packag

It depends on how you define interoperate. The way you phrase this it sounds like the only answer is the JVM. In which case: https://hackage.haskell.org/package/java-bridge https://hackage.haskell.org/package/java-bridge However in the case where there is a lot of prior Java code, it might be easier to look at Scala or even Clojure.