Contract4J is an open source developer tool that implements design by contract using Java 5 annotations (see Resources). Behind the scenes, it uses aspects to insert “advice” at the program join points (for example, calls to methods) where the tests should be evaluated, and it handles any failure of those tests by terminating program execution.
Mais, aqui
Colega aqui do trabalho me passou o link para dar uma olhada, notei que é um pouco antigo (2006), então queria saber se alguém já brincou com isso (e se sim), o que achou?