What does the Java assert keyword do, and when should it be used?

Question

What are some real life examples to understand the key role of assertions?

Answer 1

Assertion are basically used to debug the application or it is used in replacement of exception handling for some application to check the validity of an application.

Assertion works at run time. A simple example, that can explain the whole concept very simply, is herein - What does the assert keyword do in Java? (WikiAnswers).