How Does a Java HashMap Handle Collisions When Objects Have Identical Hash Codes?

HashMap Handling Collisions in Objects with Identical Hash Codes

As you correctly stated, Java HashMaps allow objects with the same hash code. This is a fundamental aspect of hash table implementations, and the HashMap manages this situation using a specific internal mechanism.

Beneath the surface, a HashMap utilizes an array of "buckets" to store key-value pairs. Each bucket corresponds to a unique identifier, which is derived from the key's hash code. When a key-value pair is added to the HashMap, the key's hash code determines the bucket in which the pair will be stored.

During retrieval, the HashMap uses the same process. It calculates the key's hash code and searches for the corresponding bucket. Within that bucket, the HashMap compares the provided key to the keys of all stored pairs using the equals() method. This comparison distinguishes between objects with identical hash codes but distinct keys.

This mechanism ensures efficient storage and retrieval of key-value pairs. Using the hash code as a bucket locator, the HashMap narrows down the search to a specific section of the bucket array. By employing the equals() method, it can further differentiate between objects within the same bucket that share hash codes.

Hence, the HashMap leverages a combination of hash codes and object equality comparisons to manage and access objects with identical hash codes, preserving both uniqueness and efficiency in its key-value storage.

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