5.2_CollectionFramework

8/6/2019 5.2_CollectionFramework

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Collections Framework


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ContentsContents

What is Collection?


Collections Hierarchy

Collections Implementations

Set

List

Map


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ObjectivesObjectives

Define a collection

Describe the collections framework

Describe the collections hierarchy

Demonstrate each collection implementation


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What is a Collection?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.


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Collections FrameworkCollections Framework

Collections Frameworkis a unified architecture formanaging collections

Main Parts of Collections Framework

1. Interfaces Core interfaces defining common functionality exhibited by

collections

2. Implementations

Concrete classes of the core interfaces providing datastructures

3. Operations Methods that perform various operations on collections


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InterfacesCollections Framework

Interfaces

Core Interface Description

Collection specifies contract that all collections should implement

Set defines functionality for a setof unique elements

SortedSet defines functionality for a setwhere elements are sorted

List defines functionality for an ordered listof non- unique elements

Map defines functionality for mapping of unique keys to values

SortedMap defines functionality for a map where its keys are sorted


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ImplementationsCollections Framework

Implementations

Set List Map

HashSet ArrayList HashMap

LinkedHashSet LinkedList LinkedHashMap

TreeSet Vector Hashtable

TreeMap

Note: Hashtable uses a lower-case t


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OperationsCollections Framework

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 Remove object from collection

Iterate collection and inspect each object

Each operation has a corresponding method implementation for eachcollection type


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Collections CharacteristicsCollections 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


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IteratorIterator

An iterator is an object used to mark a position in a

collection of data and to move from item to item within the

collection

Syntax:Iterator = .iterator();


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Set and ListCollections Hierarchy

Set and List

HashSet

Collection

SortedSet

ListSet

LinkedHashSet TreeSet LinkedList Vector ArrayList

implements

implements

implements

implements extends

extends


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MapCollections Hierarchy

Map

Map

SortedMap

Hashtable

LinkedHashMap

HashMap TreeMap

implements

implements

extends

extends


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Set : Unique things (classes that implement Set)

Map : Things with a unique ID (classes that implementMap)

List : Lists of things (classes that implement List)

Collection ImplementationsCollection Implementations

Next!


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List Implementations

ArrayListList Implementations

ArrayList

import java.util.ArrayList;

public class MyArrayList {

public static voidmain(String args[ ]) {

ArrayList alist = newArrayList( );

alist.add(new String("One"));

alist.add(new String("Two"));

alist.add(new String("Three"));

System.out.println(alist.get(0));



}}

Back!

One

Two

Three


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VectorList Implementations

Vector

import java.util.Vector;

public class MyVector {


Vector vecky = newVector( );

vecky.add(new Integer(1));



for(int x=0; x


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LinkedListList Implementations

LinkedList

import java.util.LinkedList;

public class MyLinkedList {


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


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A Set cares about uniqueness, it doesnt

allow duplicates.

SetSet

Paul

Mark

John Luke

FredPeter

TreeSetLinkedHashSetHashSet


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Set Implementations

HashSetSet Implementations

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.hasNext( )) {System.out.println(iterator.next( ));

}

}

}

Back!

d

a

c

b


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Set Implementations

LinkedHashSetSet Implementations

LinkedHashSet

import java.util.LinkedHashSet;

public class MyLinkedHashSet {

public static void main(String args[ ]) {

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


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Set Implementations

TreeSetSet Implementations

TreeSet

import java.util.TreeSet;

import java.util.Iterator;

public class MyTreeSet {


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( ));

}

}

}

Back!

Jody

Philippe

Reggie

Remiel


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A Map cares about unique identifiers.

MapMap

Paul Mark John Paul Luke

key

value

Pl Ma Jn ul Le

LinkedHashMap TreeMapHashtableHashMap


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Map Implementations

HashtableMap Implementations

Hashtable

import java.util.Hashtable;

public class MyHashtable {


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);

}

}

Back!

Table of Contents:

{address=Manila, name=Jody, id=1001}


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Map Implementations

LinkedHashMapMap Implementations

LinkedHashMap

import java.util.*;

public class MyLinkedHashMap {


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( ));

}

}

}

Back!

Jody446

Manila

Savings


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Map Implementations

TreeMapMap Implementations

TreeMap

import java.util.*;

public class MyTreeMap {

public static voidmain(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( ));

}

}

}

Back!

Printing the VALUES....

Manila

446

Jody


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Collection Classes SummaryCollection Classes Summary

NoBy indexXLinkedList

NoBy indexXVector

NoBy indexXArrayList

NoBy insertion order orlast access order

XLinkedHashSet

By natural orderor

custom comparison rules

SortedXTreeSet

NoNoXHashSet

NoBy insertion order or

last access order

XLinkedHashMap

By natural orderor

custom comparison rules

SortedXTreeMap

NoNoXHashtable

NoNoXHashMap

SortedOrderedListSetMapClass


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Key PointsKey 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.


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Questions and CommentsQuestions and Comments

5.2_CollectionFramework

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