It is natural for a developer to want to benefit from both the high-level abstractions of a language like OCaml, and the great number of libraries of a language like Java.

There are different ways to achieve this goal by leveraging existing tools and/or libraries: through communication between processes (e.g. by using JSON), through the native interfaces of both languages (i.e. by using the C language), etc. However, it is much easier, stable, and productive for the developer to have both languages share a common runtime: the JVM.

OCaml-Java provides a compiler and a runtime support to allow compilation of OCaml sources to plain Java bytecode that can then be run on any JVM. More, in order to make interoperability straighforward, OCaml-Java provides an extension to the original OCaml type system that allows the developer to manipulate Java instances directly from OCaml programs.

In this talk we will present the current state of the project, and the ongoing effort to improve performance and usability.