Topic 8. Records, enums, sealed classes, and pattern matching

Goal: learn to create validated values and closed models of alternatives, process them with exhaustive switch statements, and use stable record patterns.

Lecture contents

1. Records and immutability — Values instead of boilerplate · Compact constructors and invariants · Example 1. A monetary value · Shallow immutability and defensive copies
2. Enums — Enum defines a finite set of alternatives · Example 2. Planets with parameters
3. Sealed types and patterns — Sealed restricts direct subtypes · Type patterns, scope, and null · Example 3. Sealed shapes
4. Record patterns and deconstruction — Record patterns and deconstruction · Example 4. An arithmetic expression tree · Preview features and IDE tools

Practice and review

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