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LetsGit.IT/Categories/Java
Javamedium

What is a Java record and when would you use it?

Tags
#records#dto#immutability#boilerplate
Back to categoryPractice quiz

Answer

A record is a concise syntax for an immutable data carrier. It generates final fields, a constructor, and `equals/hashCode/toString` automatically. Use it for DTOs, messages, and value-like objects—not for entities with complex mutable lifecycle.

Advanced answer

Deep dive

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

  • Context (tags): records, dto, immutability, boilerplate
  • 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 "what-is-a-java-record-and-when-would-you-use-it?"
function explain() {
  // Start from the core idea:
  // A record is a concise syntax for an immutable data carrier. It generates final fields, a c
}

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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