Java Hashmap Under The Hood -

This is the most significant change introduced in Java 8. In older Java versions (Java 7 and earlier), collisions were always resolved using a linked list.

Think of a hotel with 16 mail slots (the buckets). When a letter arrives for room #301, you put it in slot 301 % 16 = 13 . If another letter arrives for room #605, it also goes to slot 13. Now slot 13 has a small pile of letters. The HashMap ’s job is to make finding the right letter in that pile extremely fast. java hashmap under the hood

: Allows one null key (stored at index 0) and multiple null values. This is the most significant change introduced in Java 8

) to map that large integer to a specific bucket index in the array. Handle Collisions : If the bucket is already occupied by a different key (a ), Java uses —it adds the new node to a linked list at that index. Treefication (Java 8+) When a letter arrives for room #301, you

Retrieval is much simpler. get("apple") :

Under the hood, a Java HashMap is a combination of an node objects (linked lists or trees) that uses to store and retrieve data in average time. 1. The Core Structure: Array of Buckets Internally, a HashMap maintains an array called a . Each slot in this array is known as a Default Capacity : Usually starts at 16. Node Storage : Each bucket stores a object containing four fields: the to the next node. put(key, value) When you add an entry, the JVM follows these steps: Calculate Hash : It calls the key's hashCode() method to generate an integer. Determine Index : It applies a hash function (often hash % array_length