13.12. Preconditions and Postconditions
Programmers spend significant portions of their time maintaining and debugging code. To facilitate these tasks and to improve the overall design, they generally specify the expected states before and after a method’s execution. These states are called preconditions and postconditions, respectively.
A precondition must be true when a method is invoked. Preconditions describe constraints on method parameters and any other expectations the method has about the current state of a program. If the preconditions are not met, then the method’s behavior is undefined—it may throw an exception, proceed with an illegal value or attempt to recover from the error. However, you should never rely on or expect consistent ...
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