Java™ How To Program (Early Objects), Tenth Edition

11.11 Assertions

When implementing and debugging a class, it’s sometimes useful to state conditions that should be true at a particular point in a method. These conditions, called assertions, help ensure a program’s validity by catching potential bugs and identifying possible logic errors during development. Preconditions and postconditions are two types of assertions. Preconditions are assertions about a program’s state when a method is invoked, and postconditions are assertions about its state after a method finishes.

While assertions can be stated as comments to guide you during program development, Java includes two versions of the assert statement for validating assertions programatically. The assert statement evaluates a boolean expression ...