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LetsGit.IT/Categories/Kotlin
Kotlinmedium

Sealed classes vs enums in Kotlin?

Tags
#sealed-class#enum#when#kotlin
Back to categoryPractice quiz

Answer

Enums define a fixed set of instances of one type. Sealed classes define a restricted class hierarchy where each subclass can carry different state. Both enable exhaustive when, but sealed classes are more flexible for modeling complex variants.

Advanced answer

Deep dive

Expanding on the short answer — what usually matters in practice:

  • Context (tags): sealed-class, enum, when, kotlin
  • JVM: memory (heap/stack), GC, and what drives latency.
  • Contracts: equals/hashCode/toString, mutability and consequences.
  • Performance: boxing, allocations, collections, inlining.
  • Explain the "why", not just the "what" (intuition + consequences).
  • Trade-offs: what you gain/lose (time, memory, complexity, risk).
  • Edge cases: empty inputs, large inputs, invalid inputs, concurrency.

Examples

A tiny example (an explanation template):

// Example: discuss trade-offs for "sealed-classes-vs-enums-in-kotlin?"
function explain() {
  // Start from the core idea:
  // Enums define a fixed set of constants. Sealed classes define a closed type hierarchy where
}

Common pitfalls

  • Too generic: no concrete trade-offs or examples.
  • Mixing average-case and worst-case (e.g., complexity).
  • Ignoring constraints: memory, concurrency, network/disk costs.

Interview follow-ups

  • When would you choose an alternative and why?
  • What production issues show up and how do you diagnose them?
  • How would you test edge cases?

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