This may seem like deja vu to Slashdot readers, which is what prompted me to post this. I think JSava is particularly interesting, however, because it can handle many fairly advanced features of the JVM and is capable of executing much (most?) of the JDK standard library. Some feature highlights include:
- All 200 JVM opcodes are implemented.
- JSava is complete enough to execute most major JDK library classes, such as java.util.HashMap and java.util.Random. Even some more exotic classes are mostly functional, such as java.util.concurrent.ExecutorService and company.
- Substantial support for the Reflection API. This may seem like a weird thing to support, but reflection is heavily used in the JDK library classes, so supporting it is critical in enabling complete functionality.
- All the usual Java goodness: exceptions, inheritance, interfaces, runtime error checking, etc... basically all the language features we know and love.
The JDK class files which JSava was developed with are taken from the Mac OS X 10.6 JDK (Java SE 6). The interpreter may work on Linux, but probably won't on Windows without a little bit of tweaking, particularly for I/O (it's on my todo list).
As usual, I've also created a new program page for the project. The main download link (or Dropbox mirror) provides the entire JSava runtime environment, including Rhino and JDK library classes (3.3M). If you have Java installed, running the interpreter is as easy as executing one command (no building required!). If you only want to look at the source code and not actually run the interpreter, you can also download the source only (54K).
There were a lot of engineering tricks that went into JSava and I may write about some of them in the future. However, JSava is still very much a work in progress and I plan to extend it to handle even more than it already does.