Java Interview Questions · interview question

Which practice avoids a common mistake with equals() and hashCode() Contract?

Multiple choiceMediumjava-interview-2026interviewjavapitfall

Do not base hashCode on mutable state that can change after the object enters a hash-based collection.Silence the equals() and hashCode() Contract problem by using raw types, broad catches, or shared mutable state.Ignore the equals() and hashCode() Contract issue and rely on team discipline instead of APIs or contracts.Prefer the version of equals() and hashCode() Contract that makes behavior less predictable as long as the code compiles.

Answer and explanation

Correct answer

A. Do not base hashCode on mutable state that can change after the object enters a hash-based collection.

Why

Do not base hashCode on mutable state that can change after the object enters a hash-based collection. This is a common failure mode in real Java code and a frequent interview follow-up.

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Which practice avoids a common mistake with equals() and hashCode() Contract?

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