Question

When we put a key instance say “key” and a Value instance say “value” in a HashMap class using put() method , what does the HashMap class do internally . How does it retrieve the value back when we say hashMap.get(key) ?

Edit: I do not want details here , basically trying to understand the bigger picture and the role of equals() and hashcode() method in put() and get() operations.

Answer 1

If you talk about higher picture it is just like below.Here i refer item as a key of Map

While Putting items.

1. Calculate hashcode of key
2. If basket with that hashcode is present then use the equals method on the key search the keys i that basket to determine if the element is to be added or replace.
3. If not there then create new basket (rehashing) and add that element to that.

Get:

1. Get the hashcode of key
2. Go to that basket
3. Iterate using equals on the key will return you that element from that basket.