Interview Question

Why override hashCode() when overriding equals()?

Override hashCode whenever logical equals is overridden.

💡 Concept ✅ Quick Revision ☕ Java

Answer

hashCode must be overridden with equals to preserve the Object contract for equal objects. • Hash-based collections choose buckets using hash codes before testing equality. • Equal objects with different hash codes may behave as separate keys. • A correct hash code uses the same equality-significant fields.

Example

Code

record Key(int id) {}
var set = new java.util.HashSet<Key>();
set.add(new Key(1));
System.out.println(set.contains(new Key(1)));

Output

true

Quick Revision

Override hashCode whenever logical equals is overridden.

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Previousequals() and hashCode() contract?

NextChecked vs unchecked exceptions?

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