What is the importance of the hashCode() and equals() contract?

1.	What is the importance of the hashCode() and equals() contract?
Answer» Consider the scenario of the HashMap object. We know that the Key of the HashMap uses the hashCode() and equals() methods for finding index or finding the value of a given key by uniquely identify the key-value pair in the map. If these methods are not implemented properly, then there are chances where two keys would produce the same output for these methods resulting in inaccuracy and a wrong key’s value might get updated at the time of updation. Hence, it is very much important to implement the hashCode and the equals method correctly. This can be done properly if we follow the hashCode-equals contract. The contract states that If two objects are equal, then the hashCode method should produce the same result for both objects. To ensure this, we have to override the hashCode() method whenever we override the equals() method.

Answer»

Consider the scenario of the HashMap object. We know that the Key of the HashMap uses the hashCode() and equals() methods for finding index or finding the value of a given key by uniquely identify the key-value pair in the map. If these methods are not implemented properly, then there are chances where two keys would produce the same output for these methods resulting in inaccuracy and a wrong key’s value might get updated at the time of updation. Hence, it is very much important to implement the hashCode and the equals method correctly. This can be done properly if we follow the hashCode-equals contract. The contract states that

If two objects are equal, then the hashCode method should produce the same result for both objects.
To ensure this, we have to override the hashCode() method whenever we override the equals() method.

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