1- deleration of HashMap is following
public class HashMap
implements Map
2-The HashMap gives you an unsorted, unordered Map.
3-HashMap allows one null key in a collection and multiple null values in a collection.
4-This class makes no guarantees as to the order of the map
5- Iteration over collection views requires time proportional to the "capacity" of the HashMap instance (the number of buckets) plus its size (the number of key-value mappings). Thus, it's very important not to set the initial capacity too high (or the load factor too low) if iteration performance is important.
6- HashMap has two parameter that affect its performance
1-initial capacity
2-load factor
initial capacity: capacity at the time the hash table is created .
Load Factor :if the Hash table is full ,then load factor is automatically increased the size of HashMap.
