Are you an Eiffel fan that wishes this Design By Contract stuff was available in Java?
There are a few tools out there to help, such as iContract: Design by Contract in Java.
AOP offers a nice way of working with these anal pre and post conditions ;)
Your Java code often needs to interact with external components when you develop enterprise software. Whether your application must communicate with a legacy application, an external business system, or a third-party library, using components you don’t control introduces the risk of unexpected results. IBM IT Specialist Filippo Diotalevi shows how aspect-oriented programming (AOP) can mitigate this risk by helping you design and define clear contracts between components while keeping your code clean and flexible.
Read Apply Design by Contract to Java software development with AspectJ
