What is joeq?

joeq is, simply put, a collection of compilers, interpreters, and run time routines that are designed to interface with each other. By putting together a Java compiler, a Java interpreter, and some Java run time routines, we have a complete Java virtual machine. The design is modular and language independent, so for example, you could have multiple Java compilers, or even have Java and C++ code interact transparently.

The current implementation of joeq includes a very simple Java compiler, interpreter, and run time, all written in 100% Java. Implementing the system in Java makes it very efficient, portable, and maintainable. The current implementation can correctly compile and bootstrap itself.

joeq is designed to live up to its name , meaning advanced level). The system is designed with an eye towards state-of-the-art program analysis, dynamic compilation and garbage collection techniques.

joeq is used in the CS243 "Advanced Compiling Techniques" at Stanford University to teach various topics in compilers. It is also used by various members of the SUIF Research Group at Stanford, as well as other people around the world.


joeq is designed to be a framework for performing research in the areas of compilation, program analysis, online measurement, garbage collection, and other virtual machine and compiler technology.

I started working on joeq in January 2001 in my part time because I needed an infrastructure on which to perform research, and none of the available systems were to my liking. Most compilers are static, which makes investigating dynamic compilation and online measurement difficult. Existing open-source virtual machines were not geared toward doing any kind of serious program analysis and did not support multiple languages. Finally, existing systems were written in C/C++; I find myself much more productive when writing code in Java.