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LetsGit.IT/Categories/Kotlin
Kotlineasy

Object declarations: what are they and when would you use them?

Tags
#kotlin#object#singleton#basics
Back to categoryPractice quiz

Answer

An `object` declaration defines a singleton—one instance created lazily on first access. Use it for stateless utilities or shared services when you truly need a single instance.

Advanced answer

Deep dive

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

  • Context (tags): kotlin, object, singleton, basics
  • 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 "object-declarations:-what-are-they-and-when-woul"
function explain() {
  // Start from the core idea:
  // An `object` declaration defines a singleton—one instance created lazily on first access. U
}

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?

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