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HashMap_Implementation

How to implement your own HashMap?
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   Hash Map is a implementaion of Map Interface.
   HashMap works on the principal of hashing.
-> Map.Entry interface - This interface gives a map entry (key-value pair).
   HashMap in Java stores both key and value object, in bucket, 
   as an object of Entry class which implements this nested interface Map.Entry.
-> hashCode() -HashMap provides put(key, value) for storing and get(key) method
   for retrieving Values from HashMap. When put() method is used to store (Key, Value) pair, 
   HashMap implementation calls hashcode on Key object to calculate a hash 
   that is used to find a bucket where Entry object will be stored. 
   When get() method is used to retrieve value, again key object is used to calculate a hash 
   which is used then to find a bucket where that particular key is stored.
-> equals() - equals() method is used to compare objects for equality.
   In case of HashMap key object is used for comparison, also using equals() method 
   Map knows how to handle hashing collision (hashing collision means more than 
   one key having the same hash value, thus assigned to the same bucket.
   In that case objects are stored in a linked list, 
   Where hashCode method helps in finding the bucket where that key is stored,
   equals method helps in finding the right key as there may be more than one key-value pair 
   stored in a single bucket.
** Bucket term used here is actually an index of array, that array is called table in HashMap 
   implementation. Thus table[0] is referred as bucket0, table[1] as bucket1 and so on.

So it is implementaion of HashMap

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