The HashMap also uses a technique called rehashing to ensure that the keys are evenly distributed across the buckets. If the key does not exist in HashMap, null is returned. If it does, the associated value is returned. The HashMap then checks the keys stored at that index to determine if the key exists. When a value is retrieved from the HashMap, the hash function is used to compute the index for the key.

If the key does not already exist, the key-value pair is added to the HashMap at that index. If it does, the old value is replaced with the new HashMap value. If the index is already occupied, the HashMap checks the keys stored at that index to determine if the key already exists. When a key-value pair is added to the HashMap, the hash function is used to compute the index for the key. The hash function takes the key as input and returns an integer value, which is used as the index into the array. The Java HashMap works by using a hash function to compute an index into an array of buckets or slots, where the key-value pairs are stored. Iteration: The HashMap provides methods for iterating over the key-value pairs, such as the keySet(), values(), and entrySet() methods.To overcome this, you can use the (Map m) method to obtain a synchronized (thread-safe) map. This can lead to data corruption if multiple threads modify the HashMap simultaneously. Concurrent Access: The HashMap is not synchronized, which means that multiple threads can access it simultaneously.Null Keys and Values: The HashMap allows for null keys and values, which can be useful in certain situations.This makes it a useful data structure for applications that need to store a large number of elements that may change over time. Dynamic Size: The HashMap is dynamically resizable, which means that it can grow or shrink as elements are added or removed.This allows for efficient insertion and retrieval of elements, and helps to ensure that the HashMap remains balanced as elements are added and removed. Hashing: The HashMap uses a hash function to compute an index into an array of buckets or slots, where the key-value pairs are stored.This allows you to retrieve the value associated with a given key in constant time (O(1)). Key-Value Mapping: The HashMap stores key-value pairs, where each key is associated with a single value.Some of the important features of the class include:

This allows for efficient insertion and retrieval of elements, and also helps to ensure that the HashMap remains balanced as elements are added and removed. The HashMap class uses a hash function to compute an index into an array of buckets or slots, from which the desired value can be found. It stores key-value pairs in a hash table, allowing for constant-time (O(1)) access to individual elements based on their keys. The is a class in Java that implements the Map interface.

Java hashmap example