Elena is a prototype implementation of a code generator that converts  an extension of Java including state classes ([Damiani, Giachino, Giannini and Drossopoulou, 2008] [Damiani, Giachino, Giannini and Cazzola, 2008] into Java. The syntax of the input language is Java 1.4 plus state classes and the state change expression. The syntax is given by the following diagrams.

Downloading

The current version of Elena (1.0), released (as Unlicensed Free Software -- http://unlicense.org/) in December 2010, can be obtained from here.

Example of stateJ classes from the paper from here. A solution of the Santa Claus problem using state classes can be found here.

Requirements

You will need Java 1.5 or above to run the translator (and the .java code generated).

Usage

Once downloaded you can invoke elena as follows:

extract elena.zip. You will get a directory elena containing 2 subdirectories: 1) lib (containing the .jar file to run) and 2) work (where to put the .statej files that have to be translated).

put the .statej classes to translate in the directory elena/work.

run (from the directory containing the subdirectory elena)

java -jar elena/lib/elena.jar (for windows users you can just run elena.bat)

This will produce a .java file for each of the .statej files present in the elena/work directory.

Now you can compile the .java classes using javac and use any .java standard test class to run them. The files produced are in the elena.work package and therefore they must be compiled (and run) from the root directory (the one containing elena/work).

In the samples that you download, you will find Test classes for each file.

Instrumenting the generated code

As you can see the files .java produced from the translation have a variable declared:

final static boolean VERBOSE = true;

that can be used to instrument the code to write more or less verbose messages regarding the state transitions.

A Note on Translatating .statej Subclasses

As you can see one of the examples is the class ReaderWriterFair.statej that extends ReaderWriter.statej. In order to translate ReaderWriterFair.statej in the directory elena/work must be present ReaderWriter.class (this is because the translation process uses reflection to check for presence of methods in the superclass). So if you run elena with both ReaderWriter.statej and ReaderWriterFair.statej in the directory, the first one will be translated correctly, whereas the second will be translated, but could be incorrect.

More details on the translation process

Can be found in the Master Thesis of Emanuele Cazzola (in Italian).