Is there an beautiful way to assert pre-conditions in Java methods?

Question

A lot of my functions have a whole load of validation code just below the declarations:

if ( ! (start < end) ) {
    throw new IllegalStateException( \"S         


        

Answer 1

Aspect oriented programming can be used for such a problem. Method calls can be intercepted checking for the invariant. Pointcuts and advices are configured in a declarative way. Spring and Guice make usage of AOP straightforward.

Here's an example in Guice.