http://www.openjml.org/
https://github.com/OpenJML/OpenJML

http://www.openjml.org/documentation/

articles:
http://www.eecs.ucf.edu/~leavens/JML/jmldbc.pdf

reference:
http://www.eecs.ucf.edu/~leavens/JML/jmlrefman/jmlrefman_toc.html