Topic 4. Exception handling and program debugging

Goal: learn to define error contracts, handle exceptions, preserve causes, and find logic errors with a debugger.

Lecture contents

1. Exceptions and the Throwable hierarchy — Errors as part of a contract · The Throwable hierarchy · try and catch order
2. finally, throw, and throws — finally and control flow completion · throw, throws, and preconditions
3. Custom exceptions and resources — A custom type and the original cause · Automatic resource closing
4. Checks and debugging — Assert and user data validation · Stack traces and causes · Debugging in IntelliJ IDEA · Error testing protocol

Practice and review

• Practice — 3 worked examples with complete code and output
• Tasks — 30 variants, each with tasks at three difficulty levels
• Summary — conclusions and self-check questions