Sealed classes restrict which classes can extend/implement them (`permits`). This makes class hierarchies explicit and enables exhaustive `switch` in newer Java versions. It’s useful for modeling closed sets of variants.
Advanced answer
Deep dive
Expanding on the short answer — what usually matters in practice:
Context (tags): java, sealed, inheritance, switch
JVM: memory (heap/stack), GC, and what drives latency.
Contracts: equals/hashCode/toString, mutability and consequences.
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-are-sealed-classes-in-java-and-why-use-them"
function explain() {
// Start from the core idea:
// Sealed classes restrict which classes can extend/implement them (`permits`). This makes cl
}
Common pitfalls
Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).