How is a new element inserted into the HashMap data structure?

Inserting a new element into a HashMap occurs as follows:

1. Calculate the hash code of the key using the hashCode() method.
2. Determine the bucket index in the array, using the hash code and the array size (usually through the operation hash & (capacity - 1)).
3. Check for existing elements in the selected bucket:
   • If the bucket is empty, create a new entry (Node) with the key and value.
   • If there are already elements in the bucket, traverse the linked list or tree (in newer Java versions) to find the key.
4. If the key already exists, update the value.
5. If the key is not found, add a new element to the bucket.
6. When a certain load factor threshold is reached, the array is resized and elements are redistributed (rehash).

Example of insertion:

HashMap<String, Integer> map = new HashMap<>();
map.put("key", 42);

Inside put, the process described above occurs for correct placement of the key-value pair.