Core Java · interview question
When designing an in-memory catalog using HashMap, why is it risky to use mutable objects as keys?
Multiple choiceHardchapter-4-curatedpremiumcore-javaequals-and-hashcode-in-collections
Answer and explanation
Correct answer
C. Because the hashCode might change, causing inconsistent retrieval.
Why
Using mutable objects as keys in a HashMap is risky because if the mutable fields change, the hashCode may change. This means the object might not be found in the map under its new state, leading to inconsistent retrieval and bugs in the application logic.
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