Unit 13: Exceptions and Defensive Failure Handling

Exceptions are not random punishment from Java. They are runtime evidence that an operation could not satisfy an assumption or contract.

This unit focuses on four questions:

What assumption failed?
Where did it fail?
Which layer has enough context to recover or translate the failure?
What evidence must be preserved for diagnosis?

You will use try/catch, validation, explicit exceptions, and failure messages without turning every method into a giant catch-all block.