Java for Testers - Part 233 - HashMap

In this video, I have explained and practically demonstrated the below things on HashMap Class of Collections Framework in Java:

* HashMap class is the child class of Map interface
* Groups the objects as key value pairs
* Adding key value pairs using put() method and printing them
* Duplicate Keys are not allowed, if you try to insert any duplicate key the old value will get replaced with new value
* put() - returns null when there are no duplicate keys inserted and returns the replaced value when duplication key is inserted
* Retrieving the values using get(key)
* Returns null when the provided key is not there
* Remove the values using remove(key)
* Returns the removed value
* Finding whether the key is available using containsKey(key)
* Returns boolean value
* Finding whether the value is available using containsValue(value)
* Returns boolean value
* Finding whether the HashMap is empty using isEmpty()
* Returns false when not empty
* Finding the size using size()
* Clearing all the key value pairs using clear()
* Retrieving all the keys using keySet()
* Returns Set
* Retrieving all the values using values()
* Returns Collection
* Insertion order is not preserved
* Duplicate keys are not allowed and Duplicate values are allowed
* Retrieving all the Entries using enterySet()
* Returns Set
* Using iterator() to iterate
* Entry is the inner interface of Map Interface
* getKey(), getValue() and setValue()
* Generics