Computer Notes - Multiple Inheritance

8/3/2019 Computer Notes - Multiple Inheritance

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Multiple InheritanceMultiple Inheritance

http://ecomputernotes.com


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Multiple InheritanceMultiple Inheritance

We may want to reuse characteristics of moreWe may want to reuse characteristics of more

than one parent classthan one parent class



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ExampleExample Multiple InheritanceMultiple Inheritance

Mermaid


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Mermaid

Woman Fish



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Amphibious Vehicle



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Amphibious Vehicle

Land Vehicle Water Vehicle

Vehicle

Car Boat



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Problems with Multiple InheritanceProblems with Multiple Inheritance

Increased complexityIncreased complexity

Reduced understandingReduced understanding

Duplicate featuresDuplicate features



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ProblemProblem Duplicate FeaturesDuplicate Features

Mermaid

Woman Fisheat

eat

WhichWhich eateatoperationoperation MermaidMermaidinherits?inherits?



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SolutionSolution Override the CommonOverride the Common

FeatureFeature

Mermaid

Woman Fisheat

eat

eat

Invoke eatoperation of

desired class



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ProblemProblem Duplicate FeaturesDuplicate Features

(Diamond Problem)(Diamond Problem)

WhichWhich changeGearchangeGearoperation Amphibiousoperation Amphibious

Vehicle inherits?Vehicle inherits?

Amphibious Vehicle

Land Vehicle Water Vehicle

Vehicle

Car Boat

changeGear


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Solution to Diamond ProblemSolution to Diamond Problem

Some languages disallow diamond hierarchySome languages disallow diamond hierarchy

Others provide mechanism to ignoreOthers provide mechanism to ignore

characteristics from one sidecharacteristics from one side



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AssociationAssociation

Objects in an object model interact with eachObjects in an object model interact with each

otherother

Usually an object provides services to severalUsually an object provides services to severalother objectsother objects

An object keeps associations with other objectsAn object keeps associations with other objects

to delegate tasksto delegate tasks



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Kinds of AssociationKinds of Association

Class AssociationClass Association

InheritanceInheritance

Object AssociationObject Association Simple AssociationSimple Association

CompositionComposition

AggregationAggregation



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Simple AssociationSimple Association

Is the weakest link between objectsIs the weakest link between objects

Is a reference by which one object can interactIs a reference by which one object can interactwith some other objectwith some other object

Is simply called asIs simply called asassociationassociation



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Kinds of Simple AssociationKinds of Simple Association

w.r.t navigationw.r.t navigation

OneOne--way Associationway Association

TwoTwo--way Associationway Association

w.r.t number of objectsw.r.t number of objects

Binary AssociationBinary Association

Ternary AssociationTernary Association

NN--aryaryAssociationAssociation



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OneOne--way Associationway Association

We can navigate along a single direction onlyWe can navigate along a single direction only

Denoted by an arrow towards the server objectDenoted by an arrow towards the server object



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ExampleExampleAssociationAssociation

Smith lives in a HouseSmith lives in a House

Smith Houselives-in

11



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ExampleExampleAssociationAssociation

Smith drives his CarSmith drives his Car

Smith Car drives

*1



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TwoTwo--way Associationway Association

We can navigate in both directionsWe can navigate in both directions

Denoted by a line between the associatedDenoted by a line between the associatedobjectsobjects


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ExampleExample TwoTwo--way Associationway Association

Employee Companyworks-for

1*

Employee works for companyEmployee works for companyCompany employs employeesCompany employs employees


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ExampleExample TwoTwo--way Associationway Association

Movis Smithfriend

11

Movis is a friend of SmithMovis is a friend of SmithSmith is a friend of MovisSmith is a friend of Movis


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Binary AssociationBinary Association

Associates objects of exactly two classesAssociates objects of exactly two classes

Denoted by a line, or an arrow between theDenoted by a line, or an arrow between theassociated objectsassociated objects


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ExampleExample Binary AssociationBinary Association

AssociationAssociationworksworks--forforassociates objects ofassociates objects ofexactly two classesexactly two classes

Employee Companyworks-for

1*


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ExampleExample Binary AssociationBinary Association

AssociationAssociationdrivesdrivesassociates objects of exactlyassociates objects of exactlytwo classestwo classes

Smith Car drives

*1


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Ternary AssociationTernary Association

Associates objects of exactly three classesAssociates objects of exactly three classes

Denoted by a diamond with lines connected toDenoted by a diamond with lines connected toassociated objectsassociated objects


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ExampleExample Ternary AssociationTernary Association

Objects of exactly three classes are associatedObjects of exactly three classes are associated

Student Teacher

Course

1

*

*


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ExampleExample Ternary AssociationTernary Association

Project Language

Person

Objects of exactly three classes are associatedObjects of exactly three classes are associated

*

1

*


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NN--aryaryAssociationAssociation

An association between 3 or more classesAn association between 3 or more classes

Practical examples are very rarePractical examples are very rare


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CompositionCompositionAn object may be composed of other smallerAn object may be composed of other smaller

objectsobjectsThe relationship between theThe relationship between thepartpartobjects andobjects and

thethewholewholeobject is known as Compositionobject is known as Composition

Composition is represented by a line with aComposition is represented by a line with a

filledfilled--diamond head towards the composerdiamond head towards the composer

objectobject


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ExampleExample Composition of SmithComposition of Smith

Smith

Body

Arm

Head

Leg

1

1

2 2


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ExampleExample Composition of ChairComposition of Chair

Chair

SeatArm

Back

Leg

1

12 4


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Composition is StrongerComposition is Stronger

Composition is a stronger relationship, becauseComposition is a stronger relationship, because Composed object becomes a part of the composerComposed object becomes a part of the composer

Composed object canComposed object cant exist independentlyt exist independently


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ExampleExample Composition is StrongerComposition is Stronger

Smith is made up of different body partsSmith is made up of different body parts

They canThey cant exist independent of Smitht exist independent of Smith


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ExampleExample Composition is StrongerComposition is Stronger

ChairChairs body is made up of different partss body is made up of different parts

They canThey cant exist independentlyt exist independently


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AggregationAggregationAn object may contain a collection (aggregate)An object may contain a collection (aggregate)

of other objectsof other objectsThe relationship between the container and theThe relationship between the container and the

contained object is called aggregationcontained object is called aggregation

Aggregation is represented by a line withAggregation is represented by a line with

unfilledunfilled--diamond head towards the containerdiamond head towards the container


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ExampleExampleAggregationAggregation

Room

Cupboard

Bed

Chair Table*

1

1

1


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ExampleExampleAggregationAggregation

Garden Plant*


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Aggregation is WeakerAggregation is Weaker

Aggregation is weaker relationship, becauseAggregation is weaker relationship, becauseAggregate object is not a part of the containerAggregate object is not a part of the container

Aggregate object can exist independentlyAggregate object can exist independently


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ExampleExampleAggregation is WeakerAggregation is Weaker

Furniture is not an intrinsic part of roomFurniture is not an intrinsic part of room

Furniture can be shifted to another room, andFurniture can be shifted to another room, andso can exist independent of a particular roomso can exist independent of a particular room


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ExampleExampleAggregation is WeakerAggregation is Weaker

A plant is not an intrinsic part of a gardenA plant is not an intrinsic part of a garden

It can be planted in some other garden, and soIt can be planted in some other garden, and socan exist independent of a particular gardencan exist independent of a particular garden

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Computer Notes - Multiple Inheritance