Hash study notes

Set, Data structure which does not allow duplicate elements.
Map.Entry,  is a key/value mapping contained in a Map.
Map, is a data structure consisting of a set of keys and values in which each key is mapped to a single value.
Collection, is the root of the collection hierarchy. It defines operations on data collections and the behavior that they will have in all implementations of Collections.
HashSet, is an implementation of a Set. HashSet is implemented with HashMap.


Iterator<------|
Collection<--Set<------|
Map.Entry<------------Map


Set<<-------AbstractCollection<<-|
Collection<<---——————--——-AbstractSet<<---HashSet
EntrySet-------------------^^  


Entry<<------HashMapEntry<------|
Map<<-------AbstractMap<<-----HashMap




Map is dependent of Set,Map.Entry and Collection.


Hashcode()
Entry has a method hashcode, to decide which bucket the entry is stored within a set.
? But Map is already a set, why does it still has a method hashcode?
//Because Collection has a method Hashcode(), so every class inherit it has such a method.


entrySet()

Since map is a data structure of set, so it has a method entry to return the <K,V> set.

 

HashMap has a  HashMapEntry<K, V>[] table, it's default size is 4<<<3.