Java Collection

Iterator collection over Iterator vs For-each

   Only Iterator can modify the collection
Iterator vs ListIterator

• Iterator travel only forward. ListIterator both side
• Iterator can use on List, Set, Queue but ListIterator only List

ArrayList vs Vector

• Vector is synchronized and ArrayList not
• Vector increase its size by doubling, ArrayList in 50%

ArrayList vs LinkList

• ArrayList use a dynamic array, LinkList use doubly linked list
• ArrayList Fast store and fetch data, LinkList efficient manipulation

ArryList read past
LinkList list item modify fast 

Set
HashSet Use has map (hashCode()) need to implement hashCode() and equals() //hashcode Ojbject.hash(,,)
TreeSet   Use tree Map ordered
EnumSet 

HashSet vs TreeSet
HashSet  - no order , TreeSet - ascending order

HashMap vs HashTable

•  HashTable synchronized HashMap not
• HashTable can't have null key or value but HashMap can 

Collection vs Collections

• Collection is interface and provide normal functionality
• Collections is a class to sort and synchronize collections

Fail-Fast vs Fail Safe Iteration 

Fail-Fast - throw concurrent exc - HashMap,Vector, ArrayList, HashSet

Fail-Safe - create a copy when iterator -CopyOnWriteArrayList,

ConcurrentHashMap