collection framework in java

JAVA PROGRAMMING
COLLECTION FRAMEWORK
GOVT.POLYTECHNIC
AURAI
1

CONTENTS
• Introduction
• What is Collection
• Collections Framework
•Collections Hierarchy
• Set
• List
• Map
2

COLLECTION FRAMEWORK
 The collections framework define a set of interfaces and their
implementations to manipulate collection.
The collection framework also allows us to store , retrieve, and update
a set of objects.
 It reduces programming effort while increasing performance.
It provides an API to work with the data structure, such as lists , tree,
maps, and sets.
3

The collection framework which is contained in the java.util
package is one of java’s most powerful sub-systems.
It includes implementations of these interfaces and algorithms
to manipulate them.
Which server as a container for a group of object such as a set of
words in a dictionary or a collection.
4

OBJECTIVES
Define a collection.
Describe the collections framework.
Describe the collections hierarchy.
Demonstrate each collection implementation.
5

WHAT IS A COLLECTION?
A Collection (also known as container) is an object that contains
a group of objects treated as a single unit.
Any type of objects can be stored, retrieved and manipulated as
elements of collections.
6

COLLECTIONS FRAMEWORK
Collections Framework is a unified architecture for
managing collections
Main Parts of Collections Framework
1. Interfaces
Core interfaces defining common functionality exhibited by collections
1. Implementations
Concrete classes of the core interfaces providing data structures
1. Operations
Methods that perform various operations on collections
7

COLLECTIONS FRAMEWORK INTERFACES
Collection specifies contract that all collections should implement.
Set defines functionality for a set of unique elements.
SortedSet defines functionality for a set where elements are sorted.
List defines functionality for an ordered list of non- unique elements.
Map defines functionality for mapping of unique keys to values.
SortedMap defines functionality for a map where its keys are sorted.
Core Interface Description
8

COLLECTIONS FRAMEWORK
IMPLEMENTATIONS
Set List Map
HashSet ArrayList HashMap
LinkedHashSet LinkedList LinkedHashMap
TreeSet Vector Hashtable
Tree Map
Note: Hashtable uses a lower-case “t”
9

OPERATIONS
Basic collection operations:-
• Check if collection is empty.
• Check if an object exists in collection.
• Retrieve an object from collection.
• Add object to collection. 10

• Remove object from collection
• Iterate collection and inspect each object
• Each operation has a corresponding method implementation
for each collection type
11

COLLECTIONS CHARACTERISTICS
Ordered :-
Elements are stored and accessed in a specific order.
Sorted :-
Elements are stored and accessed in a sorted order.
Indexed :-
Elements can be accessed using an index.
Unique :-
Collection does not allow duplicates.
12

ITERATOR
 The Iterator interface enables us to sequentially traverse
and access the elements contained in a collection .
 The elements of a collection can be accessed using the
methods defined by the Iterator interface.
Syntax:
Iterator <variable> = <CollectionObject>.iterator();
13

Method Defined in the Iterator Interface
Method Description
hasNext() :- Return true if the collection contains more then one element.
next() :- Returns the next element form the collection.
remove() :- Remove the current element from the collection.
14

COLLECTIONS HIERARCHY
SET AND LIST
Collection
Set List
Implements
HashSet
SortedSet
Implements
extends
LimkedHashSet TreeSet LinkedList Vector ArrayList
extends
Implements
Implements
15

COLLECTIONS HIERARCHY
MAP
Collection
Implements
Hashtable
LinkedHashMap
HashMap
extends
TreeMap
SortedMap
extends
Implements
16

COLLECTION IMPLEMENTATIONS
List:- List of things(classes that implement List)
Set:-Unique things(classes that implement set)
Map:-Things with a unique ID(classes that implement Map)
17

LIST IMPLEMENTATIONS
ARRAY LIST
Import java.util.ArrayList;
public class MyArrayList {
public static void main(string args[ ]) {
ArrayList alist=new ArrayList( );
alist.add(new string(“one”) );
alist.add(new string(“two”) );
alist.add(new string(“three”) );
system.out.println(alist.get(0) );
}
}
One
Two
Three
19

VECTOR
Import java.util.Vector;
public class MyVector {
public static void main(string args[ ]) {
Vector vecky=newVector( );
vecky.add(new Integer(1) );
for(int x=0 ; x<3 ; x++) {
system.out.println(vecky.get(x) );
}
}
}
1
2
3
20

LINKEDLIST
Import java.util.LinkedList;
public class MyLinkedList {
public static void main(string args[ ] ) {
LinkedList link=new LinkedList( );
link.add(new Double(2.0) );
link.addlast(new Double(3 .0) );
link.addfirst(new Double(1 .0) );
object array[ ] = link.toArray ( );
for( int x=0 ; x<3 ; x++) {
system.out.println( array[x] );
}
}
}
1.0
2.0
3 .0
21

SET
A set cares about uniqueness. It doesn’t allow duplicates.
“Paul”
“Peter”
“John”
“Mark”
“Luke”
“Fred”
HashSet LinkedHashSet Treeset 22

HASHSET
Import java.util.*;
public class MyHashSet {
HashSet hash=new HashSet( );
hash.add(“a” );
hash.add(“b” );
hash.add(“c”);
hash.add(“d”);
iterator iterator = hash.iterator( );
while(iterator.hashnext( ) ) {
system.out.println( iterator.next( ) );
}
}
}
d
a
c
b
23

LINKEDHASHSET
Import java.util.LinkedhashSet;
public class MyLinkedHashSet {
LinkedHashSet lhs=new LinkedHashSet( );
lhs.add(new string(“one” ) );
lhs.add(new string(“two” ) );
lhs.add(new string(“three”) );
object array = lhs.toArray[ ];
for(int x=0; x<3; x++) {
system.out.println( array[x] );
}
}
}
One
Two
Three
24

import java.util.TreeSet;
public class MyTreeSet {
public static void main(String args[ ]) {
TreeSet tree = new TreeSet();
tree.add("Jody");
tree.add("Remiel");
tree.add("Reggie");
tree.add("Philippe");
Iterator iterator = tree.iterator( );
while(iterator.hasNext( )) {
System.out.println(iterator.next( .toString( ));
}
}
}
SET IMPLEMENTATIONS
TREE SET
Jody
Philippe
Reggie
Remiel
25

A map cares about unique identifier.
Key:
Value: “Paul” “Mark” “John” “Paul” “Luke”
HashMap Hashtable LinkedHashMap
“PI” “Ma” “Jn” “ul” “Le”
TreeMap 26

MAP IMPLEMENTATIONS HASH MAP
import java.util.HashMap;
public class MyHashMap {
public static void main(String args[
]) {
HashMap map = new HashMap( );
map.put("name", "Jody");
map.put("id", new Integer(446));
map.put("address", "Manila");
System.out.println("Name:"+
map.get("name"));
System.out.println("ID: " +
map.get("id"));
System.out.println("Address: " +
map.get("address"));
}
}
Name: Jody
ID: 446
Address: Manila
27

MAP IMPLEMENTATIONS
HASH TABLE
import java.util.Hashtable;
public class MyHashtable {
public static void main(String args[ ]) {
Hashtable table = new Hashtable( );
table.put("name", "Jody");
table.put("id", new Integer(1001));
table.put("address", new String("Manila"));
System.out.println("Table of Contents:" +
table);
}
} Table of Contents:
{address=Manila, name=Jody, id=1001}28

MAP IMPLEMENTATIONS
LINKED HASH MAP
import java.util.*;
public class MyLinkedHashMap {
public static void main(String args[ ])
{
int iNum = 0;
LinkedHashMap myMap = new
LinkedHashMap( );
myMap.put("name", "Jody");
myMap.put("id", new Integer(446));
myMap.put("address", "Manila");
myMap.put("type", "Savings");
Collection values = myMap.values( );
Iterator iterator = values.iterator( );
while(iterator.hasNext()) {
System.out.println(iterator.next( ));
}
}
}
Jody
446
Manila
Savings
29

MAP IMPLEMENTATIONS
TREE MAP
import java.util.*;
public class MyTreeMap {
public static void main(String args[]) {
TreeMap treeMap = new TreeMap( );
treeMap.put("name", "Jody");
treeMap.put("id", new Integer(446));
treeMap.put("address", "Manila");
Collection values = treeMap.values()
Iterator iterator = values.iterator( );
System.out.println("Printing the
VALUES....");
while (iterator.hasNext()) {
System.out.println(iterator.next( ));
}
}
}
Printing theVALUES....
Manila
446
Jody
30

COLLECTION CLASSES SUMMARY
Class Map Set List Ordered Sorted
HashMap X No No
Hashtable X No No
TreeMap X Sorted By natural order or
custom comparison rules
LinkedHashmap X By insertion order or No
last access order
HashSet X No No
TreeSet X Sorted By natural order or
custom comparison rules
LinkedHashSet X By insertion order or No
last access order
ArrayList X By Index No
Vector X By Index No
LinkedList X By Index No
31

KEY POINTS
 Collections Framework contains:
1. Interfaces
2. Implementations
3. Operations
 A list cares about the index.
 A set cares about uniqueness, it does not allow
duplicates.
 A map cares about unique identifiers.
32

collection framework in java

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