java collection frameworks and iterator

An array is an indexed collection of fixed no of homogenous  elements
it represents same group
fixed size no increasing or decreasing


student[] s=new student[10];


Collections are growable in size
hold both homogeneous and non homogeneous
implemented based on some standard datastructure


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Arrays Collections

Fixed Growable

Mem not Recommended Mem Recommended

Only Homogeneous Hetrogeneous


no underlying Ds standard DS

noready made ready made avaialble

primitives
objects only objs

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Collection

If u Want to rpresent a Group of individual objs then go for Collection


List:


child interface of Collection

dup allows and insertion order preserved


colection

list
ArrayList
LinkedList
Vector
Stack
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Set:


child interface of Collection

dup allows insertion order not preserved

Collection

Set
HashSet    -----------LinkedHashSet
SortedSet------NavigableSet--TreeSet


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SortedSet:
      child of Interfadce of set

dup not allows only sorting order

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NavigableSet:

child inf of sortedset

provides navigation process

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Queue:
 child interface of Collection


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group of objects in key value Maps::::::::::;


Map:
Dupkeys are not allowed vals be duplicated


Map:
HashMap-------------------LinkedHashMap
IdentityHashMap----------------WeakHashMap
SortedMap-------------------NavigableMap------------TreeMap
Dictionary

 



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SortedMap:
child of Map

group of <k,v> pairs according to some order


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Navigable Map:

methods for navigation

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Collection--------------interface
collections------------class


legacy Characters:


Enumeration(i)
Dictionary(Ac)
Vector(c)
Stack(c)
HashTable(c)
Properties(c)

Methods in Collection Interface:



add(Object o)
addall()
remove()
removeall()
retainall()
clear()
containsall()
isEmpty()
size()
toArray()
iterator()



list Interface:




add(int index,Object o)
addAll()
Object get()
Object remove(int index)
Object set(int index,Obj new)
indexof()
Listitereator()




ArrayList:


dup allowed
insertion preserved

het allowed



Linkedlist::


addFirst()
last
get
remove


Vector:::::::;;




-->resizable/growable Array
-->Duplicates objects are allowed
-->Insertion order is preserved
-->Heterogeneous allowed
-->Null version is possible


add(Object o)
add(int index,Object o)
addElement(Object o)


cursors of JAVA:::


If we want to get objects one by one from the collection then we shoild go for cursor.


1.Enumeration
2.Itereator
3.ListIterator




Enumeration:

we can get Enumeration to get objects one by one from the legacy collection objects

we can create Enumeration object by using elements() method



Enumeration interface defines the following methods::


1. public boolean hasMoreElements();
2.public Object nextElement();


limitations of Enumeration::

we can use Enumeratoin only for classes and it is not universal cursor

we perform only read opeartions

we can't perform remove operations


to overcome we use Iterator