The objective of the OCaml-Java project is to allow seamless integration of OCaml and Java. Its ocamljava compiler can generate Java archives to be run on any Java virtual machine. This possibility will allow to leverage Java libraries from purely OCaml code. Moreover, the OCaml-Java runtime does not need to rely on a global runtime lock, meaning that concurrent programming is now possible in a single OCaml process.
However, versions 1.x should be regarded as mere prototypes, due to terrible performance and huge memory consumption. The upcoming 2.0 version fixes a number of issues, and greatly improves both CPU usage and memory footprint.