Mastering Java: The Ultimate Quiz for 'Thinking in Java'

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What must the hashCode() method produce?

  1. A unique identifier for each object

  2. The same value every time it is called for the same object

  3. A random number

  4. Different values for objects that are equal

The correct answer is: The same value every time it is called for the same object

The hashCode() method must produce the same value each time it is called for the same object in order to ensure consistency and accuracy when storing and retrieving objects in data structures such as HashMaps and HashSets. Option A is incorrect because hashCode() does not guarantee a unique identifier, it only ensures that equal objects have the same hash code. Option C is incorrect because a random number is not reliable for retrieving objects from data structures. Option D is incorrect because objects that are equal should have the same hashCode() value, not different values.

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