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

How Java HashMap Handles Objects with Identical Hash Codes

HashMap in Java utilizes hash codes to efficiently manage key-value pairs. While it's conceivable for different objects to possess the same hash code, the critical requirement is that if two objects are equal, their hash codes must be identical. Conversely, non-equal objects may possess varying hash codes.

Internally, HashMap employs an array of "buckets," each characterized by a unique identifier. When a key-value pair is inserted, the hash code of the key is computed and used to identify the corresponding bucket. For instance, a key with a hash code of 235 would be stored in bucket number 235.

During a value lookup, the hash code of the specified key is utilized to locate the appropriate bucket. The HashMap then iterates through the bucket and compares the key with those of the stored key-value pairs using the equals() method.

This mechanism ensures efficient key-value pair lookup. By leveraging the hash code, the HashMap can swiftly locate the correct bucket, reducing the number of comparisons required.

Consequently, it is imperative that key objects adhere to the following requirements:

• Equal keys must have identical hash codes, enabling the HashMap to store them in the same bucket.
• Non-equal keys may have identical or distinct hash codes. If two such keys share a hash code, the HashMap will utilize equals() to differentiate them.

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