Choose an ordered map when you need keys in sorted order or range queries (e.g., all keys between A and B). TreeMap provides O(log n) operations and ordering; HashMap gives O(1) average operations but no ordering.
Advanced answer
Deep dive
Expanding on the short answer — what usually matters in practice:
Context (tags): map, treemap, hashmap, ordering
Complexity: compare typical operations (average vs worst-case).
Invariants: what must always hold for correctness.
When the choice is wrong: production symptoms (latency, GC, cache misses).
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 "ordered-map-(treemap)-vs-hashmap:-when-would-you"
function explain() {
// Start from the core idea:
// Choose an ordered map when you need keys in sorted order or range queries (e.g., all keys
}
Common pitfalls
Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).