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Classification of objects

UML

Class diagrams

Sequence diagrams

Contents:

Analysis and Design

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List some important diagram types in UML

Create a class diagram

Create a sequence diagram

At the conclusion of this unit, you ill be able to:

Analysis and Design: Unit !bjecti"es

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Analysis and Design #$%

ClassificationClassification

UML & the modeling standardUML & the modeling standard

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Classification of !bjects

Real world

lcl'"ehicle lcl'people

Class creation / modeling

In the real world, there are objects, such as ar!ous a!r"lanes , cars, and "eo"le# So$e o% these

objects are er& s!$!lar, that !s, the& can be descr!bed us!n' the sa$e attr!butes or character!st!cs and

"ro!de the sa$e %unct!ons#

S!$!lar objects are 'rou"ed to'ether !n classes# (ach class !s descr!bed once, and each object !s then

created !n accordance w!th th!s blue"r!nt#

A class !s there%ore a descr!"t!on o% a )uant!t& o% objects character!*ed b& the sa$e structure and the

sa$e beha!or# +or ea$"le, the eh!cle $a.e , ### ser!al nu$ber !s an object o% the class

eh!cle# Th!s object !s there%ore a concrete !nstance o% the class#

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Different Abstractions of a Class

Car enthusiast Scrap merchant

Ma(ema(e

)ypemodel

*S

Doorsdoors

Colorcolor

Equippingequipping

Weightweight

+heelsheels

Scrap valuescrapvalue

Priceprice

lcl'"ehicle

& ma(e

&

- price

- equipping

- color

lcl'"ehicle

& ma(e

&

- weight

- scrapvalue

In th!s contet, abstract!ons are a s!$"l!%!ed re"resentat!ons o% co$"le relat!onsh!"s !n the real

world# An actuall& e!st!n' object !s abstracted to the s!'n!%!cant d!$ens!ons that are to be $a""ed#

Ins!'n!%!cant deta!ls are le%t out !n order to a!d understand!n' o% the oerall s&ste$#

Th!s ea$"le concerns cars# So%tware %or a car enthus!ast and so%tware %or a scra" $erchant conta!n

d!%%erent abstract!ons classes %or these objects#

A class can conta!n er& d!%%erent objects de"end!n' on the abstraction#

Wh!le !n one so%tware s&ste$ the classlcl_vehicledescr!bes all trans"ort eh!cles !nclud!n'

b!.es, !n another s&ste$ !t descr!bes all $otor!*ed $ach!nes w!th wheels#

oth classes hae the sa$e na$e but descr!be d!%%erent objects#

In our ea$"les, the class lcl_vehicledescr!bes all $otor!*ed eh!cles w!th / wheels#

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-epresentation of a Class

lcl'"ehicle

ma(e

modell

price

color

set'ma(e

display'attributes

increase'speed

Attributes

Class name

Methods!unctions"

Assoziationsme

Optional, does

not have to be

specified

4 notat!on6

A class !s re"resented w!th !ts na$e, attr!butes, and $ethods# W!th 4, &ou also hae the o"t!on o%

o$!tt!n' e!ther the attr!bute or the $ethod "art#

Attr!butes descr!be the data that can be stored !n the objects !n a class#

The& de%!ne the state o% an object#

4ethods descr!be the %unct!ons that can be eecuted on the data o% the object#

The& conta!n the eecutable source code and there%ore also re"resent an object7s beha!or#

AAP 8bjects eents are not !ncluded !n class d!a'ra$s#

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Classes and !bjects

lcl'"ehicle

Class:

.eneral description of objects

#blueprint%

Specifies status data #attributes%

and beha"ior #methods%

!bject #instance%: -epresentation of real orld

Specific instance of a class

Represented in course b#$

lcl'"ehicle

(5) lcl'"ehicle

or

or

A class!s a set o% objects that hae the sa$e structure and the sa$e beha!or# A class !s there%ore

l!.e a blue"r!nt, !n accordance w!th wh!ch all objects !n that class are created#

(er& objecthas an !dent!t&, a status set o% attr!bute alues, and beha!or set o% $ethods and

eents# The structure and beha!or o% s!$!lar objects are de%!ned !n the!r shared class#

Ident!t& !s an attr!bute that d!st!n'u!shes each object %ro$ all other objects# Ident!t& !s o%ten con%used

w!th ha!n' the sa$e attr!bute alues or w!th a un!)ue na$e# Two different objects can have

identical attribute values and still not be identical.

(a$"le6

Two co%%ee cu"s are the sa$e he!'ht and d!a$eter, hae the sa$e handle and are both wh!te#

Althou'h the& loo. eactl& the sa$e, the& are st!ll two se"arate cu"s#

In Ger$an l!terature on the subject o% object or!entat!on, we o%ten s"ea. o% !nstances# In objector!entat!on an !nstance !s s!$"l& an object# Another s&non&$ o% object!s instance#

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Analysis and Design #/%

ClassificationClassification

UML & the modeling standardUML & the modeling standard

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UML stands for Unified Modeling Language

0t is a global standard

0t is a language and form of notation for the specification,

construction, "isuali1ation, and documentation of models

for softare systems

Diagram types:

Class diagram

2eha"ior diagram, such as a sequence diagram

Component diagram

Distribution diagram

Modeling ith UML

4 n!%!ed 4odel!n' an'ua'e !s a standard!*ed $odel!n' lan'ua'e# It !s used %or the

s"ec!%!cat!on, construct!on, !sual!*at!on, and docu$entat!on o% $odels %or so%tware s&ste$s and

enables un!%or$ co$$un!cat!on between ar!ous users# 4 does not descr!be the ste"s !n the

object-or!ented deelo"$ent "rocess#

4 !s an !ndustr& standard and has been standard!*ed b& the 84G 8bject 4ana'e$ent Grou"

s!nce Se"te$ber 1

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34ample of a Class Diagram

lcl'rental

lcl'"ehicle

lcl'car lcl'truc( lcl'bus

lcl'boo(ing lcl'customer

lcl'heel

10..*0..*1

1

1..*1

1..*

A class d!a'ra$ descr!bes the ele$ents conta!ned !n the $odel and the!r ar!ous stat!c relat!onsh!"s#

There are two bas!c %or$s o% stat!c relat!onsh!"s6

Assoc!at!ons %or ea$"le, a car rental custo$er boo.s a car

General!*at!on ? s"ec!al!*at!on %or ea$"le, a car and a bus are both eh!cles

In class d!a'ra$s, classes can also be shown w!th the!r attr!butes and $ethods#

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Association

A customer can rent

several cars

Common cardinalities

books

Association name

* or 0..* an!

1 "#actl! one

1..* One or more

0..1 $ero or one

10..*lcl'boo(ing lcl'customer

A boo%in& refers to

a customer

An assoc!at!on descr!bes a se$ant!c relat!onsh!" between classes# The s"ec!%!c relat!onsh!" between

objects !n these classes !s .nown as an object l!n.# 8bject l!n.s are there%ore the !nstances o% an

assoc!at!on#

An assoc!at!on !s usuall& a relat!onsh!" between d!%%erent classes# Boweer, an assoc!at!on can also

be recurs!eC !n th!s case, the class would hae a relat!onsh!" w!th !tsel%# In $ost cases, recurs!e

assoc!at!ons are used to l!n. two d!%%erent objects !n one class#

The "o!nts below assu$e that the assoc!at!ons are b!nar

(ach assoc!at!on has two roles, one %or each d!rect!on o% the assoc!at!on boo.!n' custo$er,

custo$erboo.!n'# Doles can hae na$es %or ea$"le, the assoc!at!on car reserat!on could

be called reserat!on#

(ach role has a card!nal!t& that shows how $an& !nstances "art!c!"ate !n th!s relat!onsh!"# The$ult!"l!c!t& !s the nu$ber o% "art!c!"at!n' objects !n one class that hae a relat!onsh!" to an object !n

the other class#

4 notat!on6

An assoc!at!on !s re"resented b& a l!ne between the class s&$bols

The card!nal!t& o% the relat!onsh!" can be shown at each end o% the l!ne

Assoc!at!ons can be '!en a na$e %or ease o% !dent!%!cat!on a erb or a short tet# Th!s na$e !s

wr!tten !n !tal!cs aboe the l!ne and $a& hae an arrow to show the read d!rect!on# oth are

o"t!onal#

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Aggregation and Composition

Aggregation is a special

case of association, a

hole&part relationship

Composition is a specialcase of aggregation, an

e4istence&dependent

hole&part relationship

'omposition s!mbol

A&&re&ation s!mbol

lcl'rental lcl'boo(ing1..*

1

lcl'"ehicle lcl'heel1

0..*

A''re'at!on !s a s"ec!al .!nd o% assoc!at!on# A''re'at!on descr!bes one object that conta!ns another

or cons!sts o% other objects whole-"art# A eh!cle cons!sts o% wheels# The relat!onsh!" can be

descr!bed b& the words cons!sts o% or !s a "art o%#

4 notat!on %or a''re'at!on6

An a''re'at!on, l!.e an assoc!at!on, !s re"resented b& a l!ne between two classes, wh!ch then

add!t!onall& has a s$all rho$bus at one end# The rho$bus !s alwa&s at the a''re'ate end, that !s, the

whole object end# 8therw!se the notat!on conent!ons are the sa$e as %or assoc!at!ons#

@o$"os!t!on !s a s"ec!al .!nd o% a''re'at!on# @o$"os!t!on descr!bes the %act that the object

conta!ned cannot e!st w!thout the a''re'ate %or ea$"le, a car reserat!on cannot e!st w!thout the

car rental#

!%%erences to a''re'at!on6The card!nal!t& on the a''re'ate s!de can onl& be one# (ach "art !s onl& "art o% one co$"os!te object,

otherw!se the e!stence de"endenc& would be contrad!ctor The l!%et!$e o% the !nd!!dual "arts !s

l!n.ed to the l!%et!$e o% the a''re'ate6 Parts are created e!ther w!th or !$$ed!atel& a%ter the

a''re'ate, and the& are destro&ed e!ther w!th or !$$ed!atel& be%ore the a''re'ate#

4 notat!on %or co$"os!t!on6

!.e a''re'at!on, co$"os!t!on !s shown as a l!ne between two classes and $ar.ed w!th a s$all

rho$bus on the a''re'ate s!de# Boweer, !n contrast to a''re'at!on, the rho$bus !s %!lled !n#

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.enerali1ation and Speciali1ation

or

Generalization

Specialization

Generalization

Specialization

lcl'"ehicle

lcl'car lcl'truc(

lcl'"ehicle

lcl'car lcl'truc(

(nheritance arro)

4 notat!on6

General!*at!on and s"ec!al!*at!on are denoted b& tr!an'ular arrows that "o!nt %ro$ the subord!nate

class to the su"erclass#

Seeral arrows can be co$b!ned !nto a tree#

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Sequence Diagrams: 34ample

ife line

of ob+ect

'ontrol focus

Return value

1:Method (parameter)

ime

lcl'dri"er lcl'car

Process

description

(optional)

Se)uence d!a'ra$s, unl!.e class d!a'ra$s, show the d&na$!cs between objects# The& are used to

re"resent a "art!cular "rocess or a "art!cular s!tuat!on# Se)uence d!a'ra$s %ocus on the t!$e se)uence

o% the !n%or$at!on echan'e6

a @reat!on and delet!on o% objects

b 4essa'e echan'e between objects

Se)uence d!a'ra$s hae no notat!on %or re"resent!n' stat!c $ethods#

The object l!%e l!ne !s re"resented b& ert!cal dotted l!nes#

The control %ocus !s shown as a ert!cal rectan'le on the object l!%e l!ne# The control %ocus shows the

object7s act!e "er!od6

An object !s act!e when act!ons are eecuted

An object !s !nd!rectl& act!e !% !t !s wa!t!n' %or a subord!nate "rocedure to end# 4essa'es are shown as hor!*ontal arrows between the object l!nes# The $essa'e !s wr!tten aboe the

arrow !n the %or$ method (parameter)# There are ar!ous wa&s o% re"resent!n' the re"l&C !n th!s

ea$"le, the arrow !s shown as a return!n' arrow#

>ou can also !nclude a descr!"t!on o% the "rocess and add co$$ents to the object l!%e l!ne as

re)u!red#

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1: get_fuel_level( )

2: get_fuel_level( )

re_level

re_level

lcl'dri"er lcl'car lcl'tan(

re_level =fuel / fuel_max * 100.

re_level =tank->get_fuel_level( ).

Sequence Diagram: Delegation

In dele'at!on, two objects are !noled !n handl!n' a re)uest6 The rec!"!ent o% the re)uest dele'ates

the eecut!on o% the re)uest to a dele'ate#

(a$"le6

The dr!er lcl_driver calls the $ethod get_fuel_level%or the class car lcl_car# The

car cannot carr& out th!s tas. !tsel%# There%ore, the car calls the get_fuel_level$ethod %or the

class lcl_tank, that !s the car deleatesthe eecut!on o% the $ethod to the tan.#

The $a!n adanta'e o% dele'at!on as a re-use $echan!s$ l!es !n the o"t!on o% chan'!n' the

beha!or o% the rec!"!ent b& subst!tut!n' the dele'ate at runt!$e# +or ea$"le, dele'at!on enables

the car to be e)u!""ed w!th a new tan., w!thout the call chan'!n' %or the cl!ent or %or the car class#

Good enca"sulat!on o%ten %orces the use o% dele'at!on6 I% tank!n the aboe ea$"le were a "r!ate

attr!bute o% the class lcl_car, the user could not address the tan. d!rectl&, but onl& throu'h the car#

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List some diagram types in UML

Create a class diagram

Create a sequence diagram

5ou are no able to:

Analysis and Design: Summary

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0.#7 $nal%sis and &esin '(ercises

)nit* $nal%sis and &esin

To+ic* ),- Class &iara!s

At the conclus!on o% these eerc!ses, &ou w!ll be able to6

@reate a 4 class d!a'ra$

An a!rl!ne needs to $ana'e !ts a!r"lanes#

1-1 se a "enc!l and "a"er to create a 4 class d!a'ra$ that conta!ns the %ollow!n'

classes6

- A!rl!ne6 lcl_carrier

E A!r"lane 'eneral6 lcl_airplane

E Passen'er a!r"lane6 lcl_passenger_plane

E @ar'o "lane6 lcl_cargo_plane

1-1-1 Include so$e a""ro"r!ate attr!butes and $ethods %or eer& class#

1-1-2 raw l!nes to re"resent the relat!onsh!"s between the classes and !nd!cate

"oss!ble card!nal!t!es#

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)nit* $nal%sis and &esin

To+ic* ),- Class &iara!s

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Classes

!bjects

Attributes

Methods

6isibility7encapsulation

0nstantiation Constructor

.arbage collector

Contents:

*rinciples of !bject&!riented *rogramming

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Create classes

Create objects

Call methods

34plain ho the garbage collector or(s


*rinciples of !bject&!riented *rogramming: Unit!bjecti"es

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*rinciples #$%

Classes, attributes, and methodsClasses, attributes, and methods

!bjects, instances of classes!bjects, instances of classes

Accessing attributes and methodsAccessing attributes and methods

)he constructor)he constructor

Additional principlesAdditional principles

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34ample of a Class

lcl'"ehicle

*ri"ate

components

Methods:

(mplementation

*ublic

components

*ri"ate access

- "ncapsulation- .ormall! attributes

*ublic access

- (nterface

- .ormall! methods, events

ma(e

modelset'ma(e

get'ma(e

Represented in

course b#

In the 'ra"h!c, the "ubl!c co$"onent o% the class !s accessed us!n' the 'reen node or start!n' "o!nt

d!s"la&ed on the le%t# A user or cl!ent can use th!s node to access the "ubl!c co$"onents and hence

also !nd!rectl& access the "r!ate co$"onents# Boweer, the "r!ate co$"onents o% the class cannot

be addressed d!rectl& # The& are not !s!ble to the outs!de user#

Wh& are the "r!ate co$"onents o% a class h!ddenF

Th!s "r!nc!"le !s called infor!ation hidinor enca+sulationand !s used to "rotect the user#

et us assu$e that a class chan'es !ts "r!ate co$"onents, wh!le !ts !nter%ace re$a!ns unchan'ed#

An& user who s!$"l& needs to access the !nter%ace o% the class can carr& on wor.!n' w!th the class as

usual# The user does not not!ce the chan'e#

Boweer, !% an class chan'es !ts "ubl!c co$"onents, then an& user who accesses these "ubl!c

co$"onents $ust ta.e these chan'es !nto account#

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Defining Classes

CLASS ll_ve!"le #$%&'&&'.

$'#CLASS.

CLASS ll_ve!"le &+L$$'A&'.

$'#CLASS.

lcl'"ehicle

*ri"ate

components

Methodimplementation

*ubliccomponents

A%AP code

A class!s a set o% objects that hae the sa$e structure and the sa$e beha!or# A class !s there%ore

l!.e a blue+rint, !n accordance w!th wh!ch all objects !n that class are created#

The co$"onents o% the class are de%!ned !n the de%!n!t!on "art# The co$"onents are attr!butes,

$ethods, eents, constants, t&"es, and !$"le$ented !nter%aces# 8nl& $ethods are !$"le$ented !n the

!$"le$entat!on "art#

The @ASS state$ent cannot be nested, that !s, &ou cannot de%!ne a class w!th!n a class#

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Attributes

Attributes can ha"e any (ind of

data type:

C, 8, 0, *, , S)-08.

Dictionary types

User&defined types

)5*3 -39 )!

defines a reference to an

object, in this case r'car;

(5) lcl'car

PrivatePublic

make TYPE STRING,

...

r_motor

TYPE REF TO ...

(3) lcl'rental

r&car

Attr!butes descr!be the data that can be stored !n the objects o% a class#

@lass attr!butes can be o% an& t&"e6

ata t&"es6 scalar %or ea$"le data ele$ent, structured, !n tables

AAP ele$entar& t&"es @, I, ###

8bject re%erences

Inter%ace re%erences

(a$"les o% attr!butes %or the class lcl_carare6

$a.e car $a.e

$odell t&"e , $odel

serno ser!al nu$ber

color colorcart&"e estate, conert!ble, ###

$aseats nu$ber o% seats

r$otor re%erence to class lcl_motor

###

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Attributes, )ypes, and Constants: Synta4

CLASS ,laname> #$%&'&&'....

+$S: ,nrmale ef"n"t"n>.C'SA'S: ntant +$ ,te> 3AL4$ ,value>.

#AA: var"a5le1 +$ ,te>6var"a5le2 +$ ,"_te>6var"a5le7 L&8$ var"a5le16var"a5le9 +$ ,te> 3AL4$ ,value>6var"a5le +$ ,te> ;$A#-'L6

var"a5le< +$ ;$% ,laname>6var"a5le +$ ;$% ,"nterfae>.

CLASS-#AA: nl_ne +$ ... .

$'#CLASS.

In classes, &ou can onl& use the TYPEadd!t!on to re%er to data t&"es#

>ou can onl& use the LIKEre%erence %or local data objects#

The READ-ONLYadd!t!on $eans that a "ubl!c attr!bute declared w!th DATAcan be read %ro$

outs!de, but can onl& be chan'ed b& $ethods o% the class#

>ou can currentl& onl& use the READ-ONLYadd!t!on !n the "ubl!c !s!b!l!t& sect!on P!LI"

#E"TION o% a class declarat!on or !n an !nter%ace de%!n!t!on#

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+4L&C S$C&'.$$$

+;&3A$ S$C&'.#AA: make +$ tr"ng.

$'#CLASS.


+4L&C S$C&'.#AA: make +$ tr"ng.

+;&3A$ S$C&'.

$'#CLASS.

Attributes and 6isibility

*ublic attributes

Can be "ieed and

changed by all users and

in all methods

Direct access

*ri"ate attributes

Can only be "ieed and

changed from ithin the

class

8o direct access

from outside the class

>ou can "rotect attr!butes a'a!nst access %ro$ outs!de b& character!*!n' the$ as "r!ate attr!butes

de%!ned !n the PRI%ATE #E"TIOH#

Attr!butes and the!r alues that $a& be used d!rectl& b& an eternal user are "ubl!c attr!butes and are

de%!ned !n the P!LI" #E"TION#

In the aboe ea$"le %or the class lcl_car, the attr!bute make!s de%!ned as a "ubl!c attr!bute#

Publ!c attr!butes belon' to the interfaceo% the class, that !s the!r !$"le$entat!on !s "ubl!c!*ed# I% &ou

want to h!de the !nternal !$"le$entat!on %ro$ users, &ou $ust de%!ne !nternal and eternal !ews o%

attr!butes#

As a 'eneral rule, &ou should de%!ne as %ew "ubl!c attr!butes as "oss!ble#

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#.9

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Accessing *ri"ate Attributes

(5) lcl'"ehicle

*ri"ate*ublic

r&vehicle

make

Client

et_make

get_make$$$

>ou can access an object7s "r!ate attr!butes us!n' "ubl!c $ethods, wh!ch !n turn out"ut th!s attr!bute

or chan'e !t#

It !s not "oss!ble to d!rectl& access "r!ate attr!butes %ro$ outs!de %or ea$"le, $a!n "ro'ra$ or

other object# The onl& ece"t!on l!es !n the so-called %r!end conce"t, wh!ch w!ll be dealt w!th later

!n the course#

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+4L&C S$C&'.$$$

+;&3A$ S$C&'.#AA: make +$ tr"ng6

$$$

CLASS-#AA: n__ve!"le +$ ".

$'#CLASS.

0nstance Attributes and Static Attributes #$%

0nstance attributes

!ne per instance

Statement: DA)A

Static attributes

!nly one per class

Statement: CLASS&DA)A

Also (non as class

attributes

There are two .!nds o% attr!butes6

Stat!c attr!butes

Instance attr!butes

Instance attr!butes are attr!butes that e!st se"aratel& %or each object#

Instance attr!butes are de%!ned us!n' the AAP .e&word DATA#

Stat!c attr!butes e!st onl& once %or each class and are !s!ble %or all runt!$e !nstances !n that class#

Stat!c attr!butes usuall& conta!n !n%or$at!on that a""l!es to all !nstances, such as6

ata that !s the sa$e !n all !nstances

Ad$!n!strat!e !n%or$at!on about the !nstances !n that class %or ea$"le, counters, ###

Stat!c attr!butes are de%!ned us!n' the "LA##-DATA.e&word#

>ou $a& co$e across the e"ress!on class attr!butes !n docu$entat!on, howeer, the o%%!c!al ter$!n AAP 8bjects as !n @, Jaa !s stat!c attr!butes#

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#.##

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0nstance Attributes and Static Attributes #/%

Internal sessionInternal session

'lobal data ob(ects

)" lcl'"ehicle

*" lcl'"ehicle

n__ve!"le &+L$$'A&'.$?#,met!_name>.

...$'#$?#.

$'#CLASS.

CLASS ,laname> #$%&'&&'....$?#S:,met!_name>

@ &+;&' ,"m_var> +$ ,te>$B+;&' ,ex_var> +$ ,te>C?A'&' ,!_var> +$ ,te>;$4;'&' 3AL4$(,re_var>) +$ ,te>E("EPTION# )e*ce+tion,

;A&S&' ,la_exet"n> .$'#CLASS.

Methods can have

a si%nature

Methods contain the

source code& and hence

de'ine the behavior o' an

ob$ect

4ethods are !nternal "rocedures !n classes that deter$!ne the beha!or o% an object# The& can access

all attr!butes !n the!r class and can there%ore chan'e the state o% an object#

4ethods hae a "ara$eter !nter%ace called sinature that enables the$ to rece!e alues when the&

are called and "ass alues bac. to the call!n' "ro'ra$#

In AAP 8bjects, $ethods can hae IPORTIN., E(PORTIN., "/AN.IN., and RETRNIN.

"ara$eters as well as ece"t!on "ara$eters# All "ara$eters can be "assed b& alue or re%erence# As

o% SAP D?3 as!s Delease 9#10, &ou should no lon'er use the E("EPTION#"ara$eter %or

ece"t!ons but use the RAI#IN.add!t!on !nsteadC th!s w!ll be d!scussed !n $ore deta!l later#

>ou can de%!ne a return code %or $ethods us!n' RETRNIN.# >ou can onl& do th!s %or a s!n'le

"ara$eter, wh!ch add!t!onall& $ust be "assed as a alue# Also, &ou cannot then de%!ne E(PORTIN.

and "/AN.IN."ara$eters# >ou can de%!ne %unct!onal $ethods us!n' the RETRNIN."ara$eterth!s w!ll be e"la!ned !n $ore deta!l#

All !n"ut "ara$eters IPORTIN., "/AN.IN."ara$eters can be de%!ned as o"t!onal "ara$eters

!n the declarat!on us!n' the OPTIONALor DE0ALTadd!t!ons# These "ara$eters then do not

necessar!l& hae to be "assed when the object !s called# I% &ou use the OPTIONALadd!t!on, the

"ara$eter re$a!ns !n!t!al!*ed accord!n' to t&"e, whereas the DE0ALTadd!t!on allows &ou to enter

a start alue#

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Accessing *ri"ate Methods

(5) lcl'"ehicle

*ri"ate*ublic

r&vehicle

"n"t_make

et_make

make...

...

Client

4ethods also hae to be ass!'ned to a !s!b!l!t& area# Th!s deter$!nes whether the $ethods can be

called %ro$ outs!de or onl& %ro$ w!th!n the class#

It !s not "oss!ble to d!rectl& access "r!ate $ethods %ro$ outs!de# Boweer, a "r!ate $ethod can be

called b& a "ubl!c $ethod#

oth $ethod t&"es can access the "ubl!c and "r!ate attr!butes#

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Methods and 6isibility

*ublic methods

Can be called from

anyhere

*ri"ate methods

Can only be called

ithin the class

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'.$?#S: et_make "mrt"ng

"m_make +$ tr"ng.+;&3A$ S$C&'.$?#S: "n"t_make.#AA: make +$ tr"ng.

$'#CLASS.

CLASS ll_ve!"le &+L$$'A&'.$?# "n"t_make.make = Dn makeD.$'#$?#.

$?# et_make.&% "m_make &S &'&&AL.

* Calling init_make...

$LS$.make = "m_make.

$'#&%.$'#$?#.

$'#CLASS.

In th!s ea$"le, init_make!s a "r!ate $ethod that !s called b& the "ubl!c $ethod 'et_make.

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0nstance Methods and Static Methods

0nstance methods

Can use both static and instance components in their

implementation part

Can be called using an instance

Static methods

Can only use static components in their implementation

part

Can be called using the class

Rules:

Stat!c $ethods are de%!ned at class leel# The& are s!$!lar to !nstance $ethods, but w!th the

restr!ct!on that the& can onl& use stat!c co$"onents such as stat!c attr!butes !n the !$"le$entat!on

"art# Th!s $eans that stat!c $ethods do not need !nstances and can be called %ro$ an&where# The&

are de%!ned us!n' the "LA##-ET/OD#state$ent, and the& are bound b& the sa$e s&nta and

"ara$eter rules as !nstance $ethods#

The ter$ class $ethod !s co$$on, but the o%%!c!al ter$ !n AAP 8bjects as !n @, Jaa !s

stat!c $ethod#

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0nstance Methods and Static Methods: 34ample


+4L&C S$C&'.$?#S: et_make &+;&' "m_make +$ tr"ng.CLASS-$?#S: get_unt $B+;&' ex_unt +$ ".

+;&3A$ S$C&'.#AA: make +$ tr"ng.CLASS-#AA: n__ve!"le +$ ".

$'#CLASS.

CLASS ll_ve!"le &+L$$'A&'....

$?# get_unt.ex_unt = n__ve!"le.

$'#$?#

$'#CLASS.

In the stat!c $ethod get_count, &ou can onl& use the stat!c attr!bute n_o_vehicle'. All other

attr!butes o% the class are !nstance attr!butes and can onl& a""ear !n !nstance $ethods#

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Summary and UML 8otation

, re!ers to public components

- re!ers to private components

& static components are underlined


+4L&C S$C&'.$?#S: et_make &+;&' "m_make +$ tr"ng.CLASS-$?#S: get_unt $B+;&' ex_unt +$ ".

+;&3A$ S$C&'.#AA: make +$ tr"ng. ...CLASS-#AA: n__ve!"le +$ ".

$?#S: "n"t_make.$'#CLASS.

lcl'"ehicle& ma(e

& model

& n'o'"ehicles

= set'ma(e

& init'ma(e

= get'count

A 4 class d!a'ra$ shows %!rstl& the class na$e and, underneath that, the class attr!butes and

$ethods#

The !s!b!l!t& o% co$"onents !n a class !s shown !n 4 us!n' the characters and -6

!nd!cates "ubl!c co$"onents

/ !nd!cates "r!ate co$"onents

Alternat!el&, "ubl!c and "r!ate can be "re%!ed to the $ethods# The th!rd o"t!on %or "ro!ders o%

$odel!n' tools !n 4 !s to !ntroduce the!r own s&$bols %or !s!b!l!t

De"resentat!on o% !s!b!l!t& character!st!cs !s o"t!onal and !s nor$all& onl& used %or $odels that are

close to !$"le$entat!on#

Stat!c co$"onents are $ar.ed w!th an underscore#

The $ethod s!'nature !s re"resented as %ollows o"t!onal6The !n"ut and out"ut "ara$eters and the "ara$eters to be chan'ed are shown !n brac.ets#

The return code !s se"arated %ro$ the t&"e na$e b& a colon#

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*rinciples #/%






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#.#9

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Creating !bjects

Rules: !bjects are created using the C-3A)3 !2>3C)statement

!bjects can only be created and addressed using

reference "ariables

lcl'"ehicle

& ma(e

& model& ser'no

& n'o'"ehicles

= set'ma(e

& init'ma(e

= get'count

(5) lcl'"ehicle

PrivatePublic

make

meller_n...

et_makeget_unt...

C;$A$ E$C r_ve!"le

r&vehicle

A class conta!ns the 'ener!c descr!"t!on o% an object# It descr!bes all the character!st!cs that are

co$$on to all objects !n that class# ur!n' the "ro'ra$ runt!$e, the class !s used to create s"ec!%!c

objects !nstances# Th!s "rocess !s called !nstant!at!on#

(a$"le6

The s"ec!%!c object K@ar & w!th Ser-Ho# 0;15 !s created throu'h !nstant!at!on %ro$ the class

lcl_vehicleC !t !s created !n the $a!n $e$or& at runt!$e#

The lcl_vehicleclass !tsel% does not e!st as an !nde"endent runt!$e object !n AAP 8bjects#

I$"le$entat!on6

8bjects are !nstant!ated us!n' the state$ent6"REATE O!1E"T#

ur!n' !nstant!at!on, the runt!$e en!ron$ent d&na$!call& re)uests $a!n $e$or& s"ace and ass!'ns

!t to the object#

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-eference 6ariables

...

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'....

+;&3A$ S$C&'....

$'#CLASS.

CLASS ll_ve!"le &+L$$'A&'....

$'#CLASS.

#AA: r_ve!"le1 +$ ;$% ll_ve!"le6r_ve!"le2 +$ ;$% ll_ve!"le.

SA;-%_S$L$C&'.

$$$

r&vehicle+

r&vehicle)?

?

+hat do these

reference "ariables

point to?

DATA2 r_vehicle3 TYPE RE0 TO lcl_vehicledeclares a re%erence ar!able that acts as

a "o!nter to an object#

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#.2#

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Creating !bjects: Synta4


C;$A$ E$C r_ve!"le1.C;$A$ E$C r_ve!"le2.

r&vehicle+

r&vehicle)

(3) lcl'"ehicle

PrivatePublic

() lcl'"ehicle

PrivatePublic

The "REATE O!1E"Tstate$ent creates an object !n the $a!n $e$or The attr!bute alues o% th!s

object are e!ther !n!t!al alues or corres"ond to the %ALEentr

De%erence ar!ables can also be ass!'ned to each other#

+or the aboe ea$"le th!s would $ean that r_vehicle3and r_vehicle4"o!nt to the sa$e

object#

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#.22

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.arbage Collector


C;$A$ E$C r_ve!"le1.C;$A$ E$C r_ve!"le2.

r_ve!"le2 = r_ve!"le1

r&vehicle)() lcl'"ehicle

PrivatePublic

r&vehicle+

(3) lcl'"ehicle

PrivatePublic

As soon as no $ore re%erences "o!nt to an object, the Garba'e @ollector re$oes !t %ro$ the

$e$or

The Garba'e @ollector !s a s&ste$ rout!ne that auto$at!call& deletes objects that can no lon'er be

addressed %ro$ the $a!n $e$or& and releases the $e$or& s"ace the& occu"!ed#

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.arbage Collector: *rocedure

All independent references in the global main memory are chec(ed )he

references point to acti"e objects, hich are mar(ed internally

-eferences of class or instance attributes to other objects are folloed

)hese objects are also mar(ed

!bjects that are not mar(ed are deleted from the main memory

(2) lcl'object

() lcl'object

(5) lcl'object

eleted

Inde"endent re%erences are re%erences that hae not been de%!ned w!th!n a class#

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#.24

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2uffering -eferences

#AA: r_ve!"le +$ ;$% ll_ve!"le6"ta5 +$ AL$ % ;$% ll_ve!"le.

C;$A$ E$C r_ve!"le.A++$'# r_ve!"le "ta5.

C;$A$ E$C r_ve!"le.A++$'# r_ve!"le "ta5.

(2) lcl'object

(3) lcl'object

L+ A "ta5 &' r_ve!"le.* work with the current instance

$'#L+.$$$

I% &ou want to .ee" seeral objects %ro$ the sa$e class !n &our "ro'ra$, &ou can de%!ne an !nternal

table, wh!ch, %or ea$"le, onl& cons!st o% one colu$n conta!n!n' the object re%erences %or th!s class#

>ou can "rocess the objects us!n' a LOOPthrou'h the !nternal table#

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Aggregation 34ample

(5) lcl'"ehicle

PrivatePublic

"ta5_F!eel

(1) lcl'heel

(25) lcl'heel

(2*) lcl'heel

(3+) lcl'heel

I% a class de%!nes object re%erences to a second class as attr!butes !n the aboe ea$"le6 De%erences

to objects o% the class lcl_5heel, onl& these object re%erences w!ll be stored !n an object

belon'!n' to that class#

The objects !n the second class lcl_5heelhae the!r own !dent!t The& are enca"sulated !n the

%!rst class lcl_vehicleand can onl& be addressed %ro$ th!s class us!n' re%erence ar!ables#

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#.26

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*rinciples #

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#.27

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Calling Methods

(5) lcl'"ehicle

PrivatePublic

r_ve!"le->mtr_n( )

-eference

Component selector

Method

Client

m/t/r_/n

(er& object behaes !n a certa!n wa Th!s beha!or !s deter$!ned b& !ts $ethods# There are three

t&"es o% $ethod6

1# 4ethods that tr!''er the beha!or and do not return alues see ea$"le

2# 4ethods that return a alue

3# 4ethods that return or chan'e seeral alues

An object that re)u!res the ser!ces o% another object sends a $essa'e to the object "ro!d!n' the

ser!ces# Th!s $essa'e na$es the o"erat!on to be eecuted# The !$"le$entat!on o% th!s o"erat!on !s

.nown as a $ethod#

+or the sa.e o% s!$"l!c!t&, $ethod w!ll hence%orth be used as a s&non&$ %or o"erat!on and $essa'e#

The ea$"le shows the new s&nta %or $ethod calls, !n wh!ch the "ALL-ET/OD"re%! !s o$!tted#

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#.28

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Calling 0nstance Methods: Synta4

.nstance methods$CALL $?#,"ntane>->,"ntane_met!>$B+;&' ,"m_var> = ,var"a5le>

&+;&' ,ex_var> = ,var"a5le>C?A'&' ,!_var> = ,var"a5le>;$C$&3&' ,re_var> = ,var"a5le>E("EPTION# )e*ce+tion, 6 )nr,.

Shortened notation as o! 01C$ ,"ntane>->,"ntane_met!>(see online documentation) ( @a"t"n )

#AA: r_ve!"le +$ ;$% ll_ve!"le.#AA: make_name +$ S;&'.$$$

make_name = Dt!e make f t!e arD.

CALL $?# r_ve!"le->et_make $B+;&' "m_make = make_name.* other variant, since 6.1 available, see documentation!

r_ve!"le->et_make( make_name )* now getting something back from method...

r_ve!"le->get_make( &+;&' ex_make = make_name ).

Instance $ethods are called us!n' "ALL ET/OD )reference,-,)in'tance_method,#

S!nce SAP D?3 as!s Delease 9#10, the shortened %or$ !s also su""ortedC "ALL ET/OD!s o$!tted#

+or %urther !n%or$at!on, re%er to the onl!ne docu$entat!on#

S"ec!al case6 When call!n' an !nstance $ethod %ro$ w!th!n another !nstance $ethod, &ou can o$!t

the !nstance na$e# The $ethod !s auto$at!call& eecuted %or the current object#

+or the $ethod call 'et_make, &ou can o$!t the E(PORTIN.add!t!on !n the brac.ets# In th!s case,

!t !s su%%!c!ent to set the actual "ara$eter o% the caller !n the ea$"le6 make_name# Boweer, !%

the $ethod has two or $ore "ara$eters !n !ts !nter%ace, all actual and %or$al "ara$eters w!th!n the

brac.ets $ust hae the E(PORTIN.add!t!on#

In the case o% $ethods that return "ara$eters to the caller, the IPORTIN.add!t!on $ust alwa&s be

used and all actual and %or$al "ara$eters $ust be l!sted#

In $ethod calls, $ult!"le "ara$eters are se"arated b& s"aces#

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Calling Static Methods: Synta4

Static methods: CALL $?#,laname>=>,la_met!>( @a"t"n )

,laname>=>,la_met!>( @a"t"n )

#AA: r_ve!"le +$ ;$% ll_ve!"le.#AA: make_name +$ S;&'6

unt +$ &.

$$$

* get_count has one interface-parameter re_count

CALL $?# ll_ve!"le=>get_unt( &+;&' re_unt = unt ).

* other variant, since 6.1 available, see documentation

ll_ve!"le=>get_unt( &+;&' re_unt = unt ).

Stat!c $ethods also re%erred to as class $ethods are called us!n' "ALL ET/OD

)cla''name,6,)cla''_method,#

Stat!c $ethods are addressed w!th the!r class na$e, s!nce the& do not need !nstances#

Hote6

I% &ou are call!n' a stat!c $ethod %ro$ w!th!n the class, &ou can o$!t the class na$e#

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9unctional Methods

When de!ining$

!nly one -3)U-808. parameter

!nly 0M*!-)08. parameters and e4ceptions are possible

When calling$

a% -3C30608. parameters possible

b% 6arious forms of direct call possible:

M!63, CAS3, L!!*

Logical e4pressions #09, 3LS309, +@0L3, C@3C, +A0)%

Arithmetic e4pressions and bit e4pressions #C!M*U)3%,

see e4ample: a B b = c

a = 5 G 9unctional methodE2ample

4ethods that hae a RETRNIN."ara$eter are descr!bed as %unct!onal $ethods# These $ethods

cannot hae E(PORTIN.or "/AN.IN."ara$eters, but has $an& or as %ew IPORTIN.

"ara$eters and ece"t!ons as re)u!red#

+unct!onal $ethods can be used d!rectl& !n ar!ous e"ress!ons6

o'!cal e"ress!ons I0, EL#EI0, 7/ILE, "/E"K, 7AIT

The "A#Estate$ent "A#E, 7/EN

The LOOPstate$ent

Ar!th$et!c e"ress!ons "OPTE

!t e"ress!ons "OPTE

The O%Estate$ent#

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#.3#

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9unctional Methods: 34ample

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'.$?#S: get_average_fuel

&+;&' "m_"tane +$ _"tane6"m_fuel +$ t_fuel

;$4;'&'3AL4$(re_fuel) +$ t_fuel6$'#CLASS.

#AA: r_ve!"le1 +$ ;$% ll_ve!"le6r_ve!"le2 +$ ;$% ll_ve!"le6avg_fuel +$ t_fuel.

$$$

* example for short sntax in aritmet. operation

avg_fuel =r_ve!"le1->get_average_fuel( "m_"tane = 00 "m_fuel = 0 )

G r_ve!"le2->get_average_fuel( "m_"tane =

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34ternal Access to *ublic Attributes

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'.#AA: make +$ tr"ng ;$A#-'L. ou access stat!c attr!butes us!n' )cla''name,=>)cla''_attri?ute, >ou access !nstance attr!butes us!n')in'tance,->)in'tance_attri?ute, =>and ->are the co$"onent selectors

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#.33

SAP AG 2002






*rinciples #%

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#.34

SAP AG 2002

Constructor

Special method for creating

objects ith defined initial state

!nly has 0M*!-)08.

parameters and 3C3*)0!8S

0s e4ecuted only once per

instance

C;$A$ E$C

$?#S ntrutr &+;&' ,"m_arameter>$BC$+&'S ,exet"n>.

$?#S ntrutr &+;&' ,"m_arameter>$BC$+&'S ,exet"n>.

lcl'"ehicle& ma(e

& model

& n'o'"ehicles

= constructor

(3) lcl'"ehicle

PrivatePublic

The constructor !s a s"ec!al !nstance $ethod !n a class w!th the na$e con'tructor# The

%ollow!n' rules a""l&6

(ach class can hae one constructor#

The constructor !s auto$at!call& called at runt!$e w!th!n the "REATE O!1E"Tstate$ent#

I% &ou need to !$"le$ent the constructor, then &ou $ust de%!ne and !$"le$ent !t !n the

P!LI" #E"TION#

When ece"t!ons are ra!sed !n the constructor, !nstances are notcreated, so no $a!n $e$or& s"ace !s

occu"!ed#

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#.35

SAP AG 2002


+4L&C S$C&'.$?#S ntrutr &+;&' "m_make +$ tr"ng

"m_mel +$ tr"ng.+;&3A$ S$C&'.#AA: make +$ tr"ng6 Fe"g!t +$ .CLASS-#AA n__ve!"le +$ ".

$'#CLASS.

CLASS ll_ve!"le &+L$$'A&'.$?# ntrutr.make = "m_make.mel = "m_mel.A## 1 n__ve!"le.

$'#$?#.$'#CLASS.

Constructor: 34ample

#AA r_ve!"le +$ ;$% ll_ve!"le....C;$A$ E$C r_ve!"le

$B+;&' "m_make = D%errar"D"m_mel = D%90D.

Automatic constructor call

,all 'rom the

main pro%ram

>ou need to !$"le$ent the constructor when, %or ea$"le6

>ou need to allocate eternal resources

>ou need to !n!t!al!*e attr!butes that cannot be coered b& the %ALEadd!t!on to the DATA

state$ent

>ou need to $od!%& stat!c attr!butes

>ou cannot nor$all& call the constructor e"l!c!tl

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#.36

SAP AG 2002

*re"ie: Static Constructor

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'.CLASS-$?#S: CLASS_C'S;4C;.

+;&3A$ S$C&'.CLASS-#AA: n__ve!"le +$ &.

$'#CLASS.

Special static method

Automatically called before

the class is first accessed

!nly e4ecuted once per

programCLASS ll_ve!"le &+L$$'A&'.$?# CLASS_C'S;4C;.

$$$

$'#$?#. $$$$'#CLASS.

* Static Constructor is called before following statements:* demo 1

C;$A$ E$C r_ve!"le.* demo "

unter = ll_ve!"le=>n__ve!"le. if attribute is public

* demo #

ll_ve!"le=>get_unt( "mrt"ng re_unt = unter ).

The stat!c constructor !s a s"ec!al stat!c $ethod !n a class w!th the na$e cla''_con'tructor# It

!s eecuted "rec!sel& once "er "ro'ra$# The stat!c constructor o% a class )cla''name,!s called

auto$at!call& when the class !s %!rst accessed, but be%ore an& o% the %ollow!n' act!ons are eecuted6

@reat!n' an !nstance !n the class us!n' "REATE O!1E"T )o?=,, where )o?=,has the data

t&"e RE0 TO )cla''name,

Address!n' a stat!c attr!bute us!n' )cla''name,6,)attri?ute,

@all!n' a stat!c attr!bute us!n' "ALL ET/OD )cla''name,6,)cla''method,

De'!ster!n' a stat!c eent handler $ethod us!n' #ET /ANDLER)cla''name,6,)handler_method, 0OR )o?=,

De'!ster!n' an eent handler $ethod %or a stat!c eent !n class )cla''name,#

The stat!c constructor cannot be called e"l!c!tl

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#.37

SAP AG 2002

*rinciples #E%






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#.39

SAP AG 2002

)he -eference 6ariable M3

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'.$?#S ntrutr

&+;&' "m_make +$ tr"ng"m_mell +$ tr"ng.

+;&3A$ S$C&'.#AA make +$ tr"ng. $$$

$'#CLASS.

CLASS ll_ve!"le &+L$$'A&'.$?# ntrutr. H=u't a demo

#AA make +$ tr"ng 3AL4$ DenID.C'CA$'A$ "m_make make &'$->make.

$'#$?#.

$?# #4.> calling o5n method' from in'ide cla''

> call method di'+la@_attri?ute'8 9

> 5ith the 'hort '@nta* variant2

"la_attr"5ute( ).$'#$?#.

$'#CLASS.

lcl'"ehicle

*ri"ate

components

Methodimplementation

*ublic

components

Attribute

make

$->make

>ou can address the object !tsel% w!th!n !nstance $ethods us!n' the !$"l!c!tl& aa!lable re%erence

ar!able me#

escr!"t!on o% ea$"le6

In the constructor, the !nstance attr!bute make!s coered b& the locall& de%!ned ar!able make# In

order to st!ll be able to address the !nstance attr!bute, &ou need to use me#

The dumm@$ethod de$onstrates how to call a class7s own $ethod# >ou can o$!t the "re%! me-,#

8ther !$"ortant use6

An object calls another object7s $ethod and "asses !ts own address#

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#.40

SAP AG 2002

Create classes

Create objects

Call methods

34plain ho the garbage collector or(s

5ou are no able to:

*rinciples of !bject&!riented *rogramming: UnitSummary

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#.4#rinci+les of 1bject/1riented rora!!in '(ercises

)nit* rinci+les of 1bject/1riented rora!!in

To+ic* Creatin a Class


@reate a local class

An a!rl!ne needs to $ana'e !ts a!r"lanes#

,odel solution* SA+C901_A&;S_A&'_ASA+C901_A&;S_A !nclude "ro'ra$

1-1 @reate the "ac.a'e JC901_KKwhere LL6 !s &our 'rou" nu$ber and sae all there"os!tor& objects &ou hae created dur!n' the course !n th!s "ac.a'e#

1-2 @reate the $a!n "ro'ra$ JC901_KK_A&'_A&;+LA'$and the !nclude"ro'ra$ JC901_KK_A&;+LA'$the $a!n "ro'ra$ conta!ns LL6 'rou"nu$ber#

1-3 @reate the class lcl_airplane!n the !nclude "ro'ra$#

1-3-1 Th!s class has two +rivate instance attributes6

- name

-planetype#

The attr!bute %or the a!r"lane na$e should be o% the t&"e STDIHG# e%!ne

the attr!bute %or the "lane t&"e us!n' the table %!eld saplane-planetype#

1-3-2 The class has a +rivate static attribute6

- n_o_airplanes#

Th!s attr!bute should be t&"e I#

1-3-3 The class has a +ublic instance !ethodset_attributesto set the "r!ate

!nstance attr!butes na$e and "lane t&"e# (nter two corres"ond!n' !$"ort!n'

"ara$eters %or the declarat!on o% the $ethod !n the de%!n!t!on "art# The

de%!n!t!on o% these "ara$eters should be analo'ous to the two attr!butes#I$"le$ent the $ethod !n the !$"le$entat!on "artC set both attr!butes# (ach

t!$e the $ethod !s called, the stat!c attr!bute n_o_airplanesshould !ncrease

b& one# Th!s !s actuall& not r!'ht but w!ll be corrected later#

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1-3-/ The class !s to hae another +ublic instance !ethoddisplay_attributesto

d!s"la& the !nstance attr!butes# eclare th!s $ethod and, !n the

!$"le$entat!on "art, out"ut the attr!butes us!n' the WDIT( state$ent &ou

can also d!s"la& the !con !con_5'_+lane, !n wh!ch case &ou $ust add

TYPE-POOL# iconto the "ro'ra$#

1-3-5 eclare and !$"le$ent a +ublic static !ethoddisplay_n_o_airplanesto

d!s"la& the stat!c attr!bute n_o_airplanes#

In the re$a!n!n' eerc!ses !n th!s course, &ou can alwa&s start w!th the "ro'ra$ &ou

created !n the "re!ous eerc!se or co"& the corres"ond!n' $odel solut!on and cont!nue

wor.!n' w!th th!s "ro'ra$#

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'(ercises

)nit* rinci+les of 1bject/1riented

rora!!in

To+ic* nstantiatin 1bjects


Instant!ate objects

,odel solution* SA+C901_A&;S_A&'_SA+C901_A&;S_A !nclude "ro'ra$

2-1 @reate a re%erence to the class lcl_airplane#

2-2 e%!ne an !nternal table %or bu%%er!n' objects o% the class lcl_airplane# The t&"e o% the

!nternal table should there%ore beREF TO lcl_airplane#

2-3 @reate seeral objects o% the class lcl_airplaneand store the$ !n the !nternal table#

2-/ +ollow the "ro'ra$ %low !n the ebu''er#

In the re$a!n!n' eerc!ses !n th!s course, &ou can alwa&s start w!th the "ro'ra$ &ou

created !n the "re!ous eerc!se or co"& the corres"ond!n' $odel solut!on and

cont!nue wor.!n' w!th th!s "ro'ra$#

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'(ercises


rora!!in

To+ic* ,ethod Calls


@all !nstance $ethods and stat!c $ethods

,odel solution* SA+C901_A&;S_A&'_CSA+C901_A&;S_C !nclude "ro'ra$

3-1 @all the stat!c $ethod display_n_o_airplanesbe%ore !nstant!at!n' an object !n class

lcl_airplane#

3-2 se theset_attributes $ethod to set the attr!butes %or all objects alread& created#

@hoose an a!r"lane na$e and a!r"lane t&"e and "ass the$ as tet l!terals# +or the

"lane t&"e &ou can use a t&"e %ro$ the table SAPAH(, %or ea$"le K:/:-/00M#

3-3 !s"la& the object attr!butes us!n' the display_attributes$ethod#

3-/ @all the stat!c $ethod display_n_o_airplanesa second t!$e#

3-5 Add a %unct!onal stat!c $ethod 'et_n_o_airplanesto the class lcl_airplane#The

$ethod $ust be "ubl!c and hae the re_countt&"e I return "ara$eter no !n"ut

"ara$eters#

3-9 Test &our %unct!onal $ethod b& call!n' !t %ro$ the $a!n "ro'ra$#

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'(ercises

)nit* rinci+les of 1bject/1riented rora!!in

To+ic* Callin a rivate ,ethod


@all $ethods w!th!n a class

,odel solution* SA+C901_A&;S_A&'_$SA+C901_A&;S_$ !nclude "ro'ra$

5 @reate the +rivate !ethodget_technical_attributes%or the class lcl_airplane !n

&our !nclude "ro'ra$ JC901_KK_A&;+LA'$#

5-1 The a!r"lane t&"e !s the !$"ort "ara$eter# T&"e sa"lane-"lanet&"e

5-2 The e"ort "ara$eter !s the we!'ht W(IGBT and the tan. ca"ac!t& TAHO@AP#De%er to the t&"es !n the table SAPAH(#

5-3 The result, both e"ort "ara$eters are ascerta!ned !n a database access to the

table SAPAH(#

There%ore, both attr!butes are read, de"end!n' on the a!r"lane t&"e#

5-/ I% the !$"orted "lane t&"e does not e!st !n the table, set de%ault alues we!'ht

100000, tan. ca"ac!t& 10000#

5-5 Test &our $ethodget_technical_attributes6

5-5-1 & call!n' !t %ro$ the $a!n "ro'ra$

5-5-2 & call!n' !t w!th!n the display_attributes$ethod

5-3-3 Wh!ch call was success%ul, and wh&F

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#.42rinci+les of 1bject/1riented rora!!in olutions


rora!!in

To+ic* Creatin a Class

>--------------------------------------------------------------------->

> Re+ort #AP!"B;3_AIR#_AIN_a >

>--------------------------------------------------------------------->

;$+; a5901_a"r_ma"n_a.

+$-+LS "n.

&'CL4#$ SA+C901_a"r_A.

>----------------------------------------------------------------->

> Include #AP!"B;3_AIR#_A >

>----------------------------------------------------------------->

>------------------------------------------------------------------>

> "LA## lcl_air+lane DE0INITION >

>------------------------------------------------------------------>

CLASS ll_a"rlane #$%&'&&'.

+4L&C S$C&'.

-------------------------------- C'SA'S: _1 +$ " 3AL4$ 70.

$?#S: et_attr"5ute &+;&'

"m_name +$ tr"ng

"m_lanete +$ alane-lanete6

"la_attr"5ute.

CLASS-$?#S: "la_n__a"rlane.

+;&3A$ S$C&'. ----------------------------------

#AA: name +$ tr"ng6

lanete +$ alane-lanete.

CLASS-#AA: n__a"rlane +$ ".

$'#CLASS.

>------------------------------------------------------------------>

> "LA## lcl_air+lane IPLEENTATION >

>------------------------------------------------------------------>

CLASS ll_a"rlane &+L$$'A&'.

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$?# et_attr"5ute.

name = "m_name.

lanete = "m_lanete.

n__a"rlane = n__a"rlane G 1.

$'#$?#.

$?# "la_attr"5ute.

M;&$: / "n_F_lane a "n6

/ D'ame f a"rlane:D(001)6 A _1 name6

/ DA"rlane teD(002)6 A _1 lanete.

$'#$?#.

$?# "la_n__a"rlane.

M;&$: /6 / Dtal num5er f laneD(a1)6

A _1 n__a"rlane L$%-E4S&%&$#6 /.

$'#$?#.

$'#CLASS.

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olutions


rora!!in

To+ic* nstantiatin 1bjects

>--------------------------------------------------------------------->

> Re+ort #AP!"B;3_AIR#_AIN_? >

>--------------------------------------------------------------------->

> create and in'ert +lane' into internal ta?le >

>--------------------------------------------------------------------->

REPORT 'a+?cB;3_air'_main_?$

TYPE-POOL# icon$

IN"LDE #AP!"B;3_air'_A$

#AA: r_lane +$ ;$% ll_a"rlane6

lane_l"t +$ AL$ % ;$% ll_a"rlane.

#TART-O0-#ELE"TION$

>CCCCCCCCCCCCCCCCCCCCCCCCCCCCCC

C;$A$ E$C r_lane. A++$'# r_lane lane_l"t.

C;$A$ E$C r_lane.

A++$'# r_lane lane_l"t.

C;$A$ E$C r_lane.


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olutions


rora!!inTo+ic* ,ethod Calls

>--------------------------------------------------------------------->

> Re+ort #AP!"B;3_AIR#_AIN_" >

>--------------------------------------------------------------------->

> call method 'et_Attri?ute' to initialie o?=ect' >

> and vi'ualie content of o?=ect' via di'+la@_attri?ute' >

>--------------------------------------------------------------------->

REPORT 'a+?cB;3_air'_main_c$

TYPE-POOL# icon$

IN"LDE 'a+?cB;3_air'_c$


lane_l"t +$ AL$ % ;$% ll_a"rlane6

unt te ".

#TART-O0-#ELE"TION$


ll_a"rlane=>"la_n__a"rlane( ).

C;$A$ E$C r_lane.


r_lane->et_attr"5ute( "m_name = DL? erl"nD

"m_lanete = D9-900D ).

C;$A$ E$C r_lane.


r_lane->et_attr"5ute( "m_name = DAA 'eF rkD

"m_lanete = D7-100D ).

L+ A lane_l"t &' r_lane.

r_lane->"la_attr"5ute( ).

$'#L+.

ll_a"rlane=>"la_n__a"rlane( ).

* calling the functional method get_n_o_airplanes

* long sntax for functional call$

* lcl_airplane%&get_n_o_airplanes' receiving re_count % count (.

* short sntax for functional call$

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unt = ll_a"rlane=>get_n__a"rlane( ).

Fr"te: / D'um5er f a"rlane : D6 unt.

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>--------------------------------------------------------------------->

> Include #AP!"B;3_AIR#_" >

> Develo+' functional 'tatic method get_n_o_air+lane' >

>--------------------------------------------------------------------->

>------------------------------------------------------------------>

> "LA## lcl_air+lane DE0INITION >>------------------------------------------------------------------>

CLASS ll_a"rlane #$%&'&&'.

+4L&C S$C&'.

--------------------------------

C'SA'S: _1 +$ " 3AL4$ 70.

$?#S: et_attr"5ute &+;&'

"m_name +$ tr"ng


"la_attr"5ute.

CLASS-$?#S: "la_n__a"rlane6

get_n__a"rlane return"ng 3AL4$(re_unt) te &.

+;&3A$ S$C&'.

----------------------------------

#AA: name +$ tr"ng6

lanete +$ alane-lanete.

CLASS-#AA: n__a"rlane +$ ".

$'#CLASS.

>------------------------------------------------------------------>


>------------------------------------------------------------------>

CLASS ll_a"rlane &+L$$'A&'.

$?# et_attr"5ute.

name = "m_name. lanete = "m_lanete.


$'#$?#.

$?# "la_attr"5ute.

M;&$: / "n_F_lane a "n6

/ D'ame f a"rlane:D(001)6 A _1 name6

/ DA"rlane teD(002)6 A _1 lanete.

$'#$?#.

$?# "la_n__a"rlane.

M;&$: /6 / Dtal num5er f laneD(a1)6

A _1 n__a"rlane L$%-E4S&%&$#6 /.

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$'#$?#.

met! get_n__a"rlane.

re_unt = n__a"rlane.

enmet!.

$'#CLASS.

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olutions


rora!!in

To+ic* Constructor>--------------------------------------------------------------------->

> Re+ort #AP!"B;3_AIR#_AIN_d >

>--------------------------------------------------------------------->

> call con'tructor of cla'' lcl_air+lane >

>--------------------------------------------------------------------->

REPORT 'a+?cB;3_air'_main_d$

TYPE-POOL# icon$

IN"LDE 'a+?cB;3_air'_d$



#TART-O0-#ELE"TION$


lcl_air+lane6,di'+la@_n_o_air+lane'8 9$

C;$A$ E$C r_lane exrt"ng "m_name = DL? erl"nD

"m_lanete = D9-900D.

APPEND r_+lane TO +lane_li't$

C;$A$ E$C r_lane exrt"ng "m_name = DAA 'eF rkD

"m_lanete = D7-100D.

LOOP AT +lane_li't INTO r_+lane$

r_+lane-,di'+la@_attri?ute'8 9$

ENDLOOP$


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>--------------------------------------------------------------------->

> Include #AP!"B;3_AIR#_d >

>--------------------------------------------------------------------->

>------------------------------------------------------------------>


>------------------------------------------------------------------>

"LA## lcl_air+lane DE0INITION$

P!LI" #E"TION$

--------------------------------

"ON#TANT#2 +o'_3 TYPE i %ALE F;$

$?#S: ntrutr &+;&'

"m_name +$ tr"ng


"la_attr"5ute.

"LA##-ET/OD#2 di'+la@_n_o_air+lane'$

PRI%ATE #E"TION$

----------------------------------

DATA2 name TYPE 'tringG

+lanet@+e TYPE 'a+lane-+lanet@+e$

"LA##-DATA2 n_o_air+lane' TYPE i$

END"LA##$

>------------------------------------------------------------------>


>------------------------------------------------------------------>

"LA## lcl_air+lane IPLEENTATION$

$?# ntrutr.

name = "m_name.

lanete = "m_lanete.


$'#$?#.

ET/OD di'+la@_attri?ute'$

7RITE2 H icon_5'_+lane a' iconG

H Name of air+lane8;;39G AT +o'_3 nameG

H Air+lane t@+e2 8;;49G AT +o'_3 +lanet@+e$

ENDET/OD$

ET/OD di'+la@_n_o_air+lane'$

7RITE2 HG H Num?er of air+lane'2 8ca39G

AT +o'_3 n_o_air+lane' LE0T-1#TI0IEDG H$

ENDET/OD$

END"LA##$

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olutions


rora!!in

To+ic* Callin a rivate ,ethod

>--------------------------------------------------------------------->

> Re+ort #AP!"B;3_AIR#_AIN_e >

> >

>--------------------------------------------------------------------->

> in'ide di'+la@_attri?ute' a +rivate method i' called to get >

> further detail' on technical a'+ect' of the +lanet@+e >

>--------------------------------------------------------------------->

REPORT 'a+?cB;3_air'_main_e$

TYPE-POOL# icon$

IN"LDE 'a+?cB;3_air'_e$

DATA2 r_+lane TYPE RE0 TO lcl_air+laneG

+lane_li't TYPE TA!LE O0 RE0 TO lcl_air+lane$

#TART-O0-#ELE"TION$



"REATE O!1E"T r_+lane e*+orting im_name 6 L/ !erlin

im_+lanet@+e 6 JBJ-B;;$

APPEND r_+lane TO +lane_li't$


"REATE O!1E"T r_+lane e*+orting im_name 6 AA Ne5 York

im_+lanet@+e 6 J4J-4;;$



>--------------------------------------------------------------------->

> Include #AP!"B;3_AIR#_e >

>--------------------------------------------------------------------->

>------------------------------------------------------------------>


>------------------------------------------------------------------>

"LA## lcl_air+lane DE0INITION$

P!LI" #E"TION$

--------------------------------

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"ON#TANT#2 +o'_3 TYPE i %ALE F;$

ET/OD#2 con'tructor IPORTIN.

im_name TYPE 'tring

im_+lanet@+e TYPE 'a+lane-+lanet@+eG

di'+la@_attri?ute'$

"LA##-ET/OD#2 di'+la@_n_o_air+lane'$

PRI%ATE #E"TION$

----------------------------------

$?#S: get_te!n"al_attr"5ute

&+;&' "m_te te alane-lanete

$B+;&' ex_Fe"g!t +$ _lan_Fe"

ex_tanka +$ _aa"t.

DATA2 name TYPE 'tringG

+lanet@+e TYPE 'a+lane-+lanet@+e$

"LA##-DATA2 n_o_air+lane' TYPE i$

END"LA##$ lcl_air+lane DE0INITION

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>------------------------------------------------------------------>


>------------------------------------------------------------------>

"LA## lcl_air+lane IPLEENTATION$

ET/OD con'tructor$ name 6 im_name$

+lanet@+e 6 im_+lanet@+e$

n_o_air+lane' 6 n_o_air+lane' 3$

ENDET/OD$ con'tructor

ET/OD di'+la@_attri?ute'$

data2 5eight t@+e 'a+lane-5eightG

ca+ t@+e 'a+lane-tankca+$

7RITE2 H icon_5'_+lane A# I"ONG

H Name of air+lane8;;39G AT +o'_3 nameG

H Air+lane t@+e2 8;;49G AT +o'_3 +lanet@+e$

get_technical_attri?ute'8 e*+orting im_t@+e 6 +lanet@+e

im+orting e*_5eight 6 5eight

e*_tankca+ 6 ca+ 9$

5rite2 H 5height2 8;;F9G 5eightG

tankca+2 8;;B9G ; ca+$

ENDET/OD$ di'+la@_attri?ute'

ET/OD di'+la@_n_o_air+lane'$

7RITE2 HG H Num?er of air+lane'2 8ca39G

AT +o'_3 n_o_air+lane' LE0T-1#TI0IEDG H$ ENDET/OD$ di'+la@_n_o_air+lane'

$?# get_te!n"al_attr"5ute.

S$L$C S&'L$ Fe"g!t tanka %; alane

&' (ex_Fe"g!t6 ex_tanka)

M?$;$ lanete = "m_te.

&% -u5r ,> 0.

ex_Fe"g!t = 100000.

ex_tanka = 10000.

$'#&%. $'#$?#. get_te!n"al_attr"5ute

END"LA##$ lcl_air+lane IPLEENTATION

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2

SAP AG 2002

.enerali1ation 7 speciali1ation of classes

Contents:

0nheritance

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2.2

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Define an inheritance relationship beteen

classes

-edefine methods


0nheritance: Unit !bjecti"es

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2.3

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lcl'truc(

& ma4'cargo

& n'o'tan(s

& n'o'heels

=

=get'cargo

0nheritance: UML 34ample

lcl'"ehicle

& ma(e

& modell

& ser'no

& color

& n'o'"ehicles

=constructor

=display'attributes

=get'count

lcl'car

& car'type

& ma4'seats

& accelertion

=

=get'type

lcl'bus

& ma4'passengers

& la"atory

& tele"ision

=

=get'passengers

-is a-

relationship

Inher!tance !s a relat!onsh!", !n wh!ch one class the subclass !nher!ts all the $a!n character!st!cs o%

another class the su"erclass# The subclass can also add new co$"onents attr!butes, $ethods, and

so on and re"lace !nher!ted $ethods w!th !ts own !$"le$entat!ons#

Inher!tance !s an !$"le$entat!on relat!onsh!" that e$"has!*es s!$!lar!t!es between classes# In the

ea$"le aboe, the s!$!lar!t!es between the car, bus, and truc. classes are etracted to the eh!cle

su"erclass# Th!s $eans that co$$on co$"onents are onl& de%!ned?!$"le$ented !n the su"erclass and

are auto$at!call& "resent !n the subclasses#

The !nher!tance relat!onsh!" !s o%ten descr!bed as an !s a relat!onsh!"6 A truc. is aeh!cle#

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2.4

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Multiple 0nheritance?

Specialization

Generalization

3o

multiple inheritance

lcl'super$ lcl'super/

lcl'sub$ lcl'sub/ lcl'subou can, howeer, s!$ulate $ult!"le !nher!tance !n AAP 8bjects us!n' !nter%aces see the sect!on

on !nter%aces#

S!n'le !nher!tance does not $ean that the !nher!tance tree onl& has one leel# 8n the contrar&, the

d!rect su"erclass o% one class can !n turn be the subclass o% a %urther su"erclass# In other words6 The

!nher!tance tree can hae an& nu$ber o% leels, so that a class can !nher!t %ro$ seeral su"erclasses,

as lon' as !t onl& has one d!rect su"erclass# Inher!tance !s a one-s!ded relat!onsh!"6 Subclasses .now the!r d!rect su"erclasses, but

su"erclasses do not .now the!r subclasses#

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2.6

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0nheritance: Synta4


+4L&C S$C&'.$?#S: et"mate_fuel

&+;&' "m_"tane +$ _"tane;$4;'&' 3AL4$(re_fuel) +$ t_fuel.

+;&3A$ S$C&'.#AA: make +$ tr"ng6

$$$

$'#CLASS.

CLASS ll_truk #$%&'&&' &'?$;&&' %;ll_ve!"le.

+4L&C S$C&'.$?#S: get_arg ;$4;'&' 3AL4$(re_arg) +$ t_arg.

+;&3A$ S$C&'.#AA: max_arg +$ t_arg.

$'#CLASS.

Hor$all& the onl& other entr& re)u!red %or subclasses !s what has chan'ed !n relat!on to the d!rect

su"erclass# 8nl& additionsare "er$!tted !n AAP 8bjects, that !s, !n a subclass &ou can neer ta.e

so$eth!n' awa& %ro$ a su"erclass# All co$"onents %ro$ the su"erclass are auto$at!call& "resent !n

the subclass#

The attr!butes o% the su"erclass lcl_vehiclee!st !n the subclass lcl_truckC the $ethod

e'timate_fuel!s also aa!lable !n the subclass#

The subclass de%!nes a $ethod get_cargo# It !s not !s!ble !n the su"erclass#

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2.7

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CLASS ll_truk &+L$$'A&'.$?# et"mate_fuel.

...uer->et"mate_fuel(...)

$'#$?#.$'#CLASS.

-edefining Methods

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'.$?#S et"mate_fuel

&+;&' "m_"tane +$ t_"tane;$4;'&' 3AL4$(re_fuel) +$ t_fuel.

$'#CLASS.

CLASS ll_truk #$%&'&&' &'?$;&&' %; ll_ve!"le.+4L&C S$C&'.$?#S et"mate_fuel ;$#$%&'&&'....

$'#CLASS.

,annot chan%ethe inter'ace

.e/

implementation o'

method0l/a!s points to the

superclass component

The REDE0INITIONstate$ent %or the !nher!ted $ethod $ust be !n the sa$e #E"TIONas the

de%!n!t!on o% the or!'!nal $ethod# It can there%ore not be !n the PRI%ATE #E"TION, s!nce a class7s

"r!ate $ethods are not !s!ble and there%ore cannot be rede%!ned !n subclasses#

I% &ou rede%!ne a $ethod, &ou do not need to enter !ts !nter%ace a'a!n !n the subclass, but onl& the

na$e o% the $ethod# The reason %or th!s !s that AAP 8bjects does not su""ort oerload!n'#

In the case o% rede%!ned $ethods, chan'!n' the !nter%ace overloadin !s not "er$!ttedC ece"t!on6

8erload!n' !s "oss!ble w!th the constructor#

W!th!n the rede%!ned $ethod, &ou can access co$"onents o% the d!rect su"erclass us!n' the #PER

re%erence#

To !$"le$ent a rede%!ned $ethod !n a subclass, &ou o%ten need to call the $ethod o% the sa$e na$e

!n the immediatesu"erclass# In AAP 8bjects &ou can call the $ethod %ro$ the su"erclass us!n' the"seudo-re%erence 'u+er6

The "seudo-re%erence 'u+ercan onl& be used !n rede%!ned $ethods#

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2.8

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0nheritance and -edefining the Constructor

CLASS ll_ve!"le #$%&'&&'.+4L&C S$C&'.$?#S: ntrutr &+;&'

"m_make +$ tr"ng.$'#CLASS.

CLASS ll_truk #$%&'&&' &'?$;&&' %; ll_ve!"le.+4L&C S$C&'.$?#S: ntrutr &+;&' "m_make +$ tr"ng

"m_arg +$ t_arg.+;&3A$ S$C&'.#AA: max_arg +$ t_arg.

$'#CLASS.

CLASS ll_ve!"le &+L$$'A&'.$?# C'S;4C;.make = "m_make.$'#$?#.

$'#CLASS.

CLASS ll_truk &+L$$'A&'.$?# ntrutr.

CALL $?# uer->ntrutr( "m_make = "m_make ).max_arg = "m_arg.$'#$?#.

$'#CLASS.

,an chan%e theinter'ace

,all constructor o' immediate

superclass

The constructor o% the su"erclass !ustbe called w!th!n the constructor o% the subclass# The reason

%or th!s !s the s"ec!al %unct!on o% the constructor6 To ensure that objects are !n!t!al!*ed correctl 8nl&

the class !tsel%, howeer, can !n!t!al!*e !ts own "r!ate co$"onents correctl&C th!s tas. cannot be

carr!ed out b& the subclass# There%ore !t !s essent!al that all !nstance constructors are called !n an

!nher!tance h!erarch& !n the correct se)uence#

+or stat!c constructors, unl!.e !nstance constructors, the stat!c constructor !n the su"erclass !s called

auto$at!call&, that !s the runt!$e s&ste$ auto$at!call& ensures that the stat!c constructors o% all !ts

su"erclasses hae alread& been eecuted be%ore the stat!c constructor !n a "art!cular class !s eecuted#

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+4L&C S$C&'. $$$

+;$C$# S$C&'.#AA tank +$ ;$% ll_tank.

+;&3A$ S$C&'.#AA make +$ tr"ng.

$'#CLASS.

0nheritance and 6isibility

*ublic components

6isible to all

Direct access

*rotected components

!nly "isible ithin the class

and its subclasses

*ri"ate components

!nly "isible ithin the class

8o access from outside the

class,

not e"en from the subclass

lcl'"ehicle& ma(e

& modell

G tan(

...

=constructor

=display'attributes

=get'count

, public

4 protected

- private

Inher!tance "ro!des an etens!on o% the !s!b!l!t& conce"t6 There are "rotected co$"onents# The

!s!b!l!t& o% these co$"onents l!es between that o% the "ubl!c co$"onents !s!ble to all users, all

subclasses, and the class !tsel%, and "r!ate !s!ble onl& to the class !tsel%# Protected co$"onents

are !s!ble to and can be used b& all subclasses and the class !tsel%#

Subclasses cannot access the "r!ate co$"onents "art!cularl& attr!butes o% the su"erclass# Pr!ate

co$"onents are 'enu!nel& "r!ate# Th!s !s "art!cularl& !$"ortant !% a su"erclass needs to $a.e local

enhance$ents to handle errors6 It can use "r!ate co$"onents to do th!s w!thout .now!n' or

!nal!dat!n' subclasses#

In AAP 8bjects, &ou $ust .ee" to the sect!on se)uence P!LI", PROTE"TED, PRI%ATE#

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2.##

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(5) lcl'bus

PrivatePublic

Protected

,an be addressed

-'rom outside- 'or

all clients

,an onl! be

addressed /ithin

the class

Inherited

tank

get_makeet_makeget_unt"la_attr"5uteet"mate_fuel

Inherited

6isibility of *rotected Components

In th!s ea$"le, lcl_?u', a subclass o% lcl_vehicle, can d!rectl& access the "rotected attr!bute

tank# I% the attr!bute was "r!ate, the subclasses would onl& be able to access tankus!n' non-

"r!ate $ethods#

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2.#2

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-ules for -edefining Methods

0nherited methods can be redefined in subclasses -edefined methods must be re&implemented in subclasses

)he signature of redefined methods cannot be changed

Static methods cannot be redefined

0n inheritance, static components are FsharedF:

A class shares its non&pri"ate static attributes ith all its subclasses

lcl'"ehicles

lcl'car lcl'truc( lcl'bus

et"mate_fuel

5he method is implemented in di!!erent wa#s

et"mate_fuel et"mate_fuel et"mate_fuel

In AAP 8bjects, &ou can not onl& add new co$"onents, but also "ro!de !nher!ted $ethods w!th

new !$"le$entat!ons# Th!s !s .nown as redefinition# >ou can onl& rede%!ne "ubl!c and "rotected

!nstance $ethods, other co$"onents stat!c $ethods, attr!butes and so on cannot be rede%!ned#

@han'es to $ethod "ara$eters s!'nature chan'es are not "oss!ble#

In 4, the rede%!n!t!on o% a $ethod !s re"resented b& l!st!n' the $ethod a'a!n !n the subclass#

4ethods and all other co$"onents that are !nher!ted but not rede%!ned are not l!sted !n the subclass,

as the!r e!stence there !s clear %ro$ the s"ec!al!*at!on relat!onsh!"#

>ou should not con%use rede%!n!t!on w!th oerload!n'# The latter descr!bes the ab!l!t& o% a class to

hae $ethods w!th the sa$e na$e but a d!%%erent s!'nature# Th!s !s not aa!lable !n AAP 8bjects#

There !s onl& one stat!c eent "er roll area# In th!s wa&, a class that de%!nes a "ubl!c or "rotected

stat!c attr!bute shares th!s attr!bute w!th all !ts subclasses# The s!'n!%!cant "o!nt here !s that subclassesdo not each rece!e the!r own co"& o% the stat!c attr!bute#

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2.#3

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-edefining Methods: 34ample

$?# et"mate_fuel.#AA: ttal_Fe"g!t ...> =u't an e*am+leM

ttal_Fe"g!t = max_arg GFe"g!t.

re_fuel = ttal_Fe"g!t *"m_"tane * fatr.

$'#$?#.

$?# et"mate_fuel.#AA: ttal_Fe"g!t ...> =u't an e*am+leM

ttal_Fe"g!t = max_aenger *average_Fe"g!t G Fe"g!t.

re_fuel = ttal_Fe"g!t *"m_"tane * fatr.

$'#$?#.

lcl'bus

& ma4'passengers

...

= constructor

= estimate'fuel

lcl'truc(

& ma4'cargo

...

= constructor

= estimate'fuel

In the aboe ea$"le, both rede%!ned $ethods calculate the return code !n d!%%erent wa&s# The

!$"ortant "o!nt !s that the se$ant!cs sta& the sa$e#

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2.#4

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Define an inheritance relationship beteen

classes

-edefine methods

5ou are no able to:

0nheritance: Unit Summary

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2.#5 nheritance

'(ercises

)nit* nheritance

To+ic* Creatin Class ierarchies


e%!ne subclasses

Dede%!ne su"erclass $ethods !n subclasses

,odel solution* SA+C901_&'?S_A&'_A

SA+C901_&'?S_A !nclude "ro'ra$

our +rora!* JC901_KK_A&'_A&;+LA'$JC901_KK_A&;+LA'$ !nclude "ro'ra$

1-1 4a.e both !nstance attr!butes o% the class lcl_airplane!s!ble to the!r subclasses

PDI=AT( S(@TI8H - PD8T(@T( S(@TI8H#

1-2 @reate the subclass lcl_passenger_plane%or the class lcl_airplane# Also, create

th!s subclass !n &our !nclude "ro'ra$#

1-2-1 The class !s to hae a "r!ate !nstance attr!bute ma!_seatsw!th the sa$e

t&"e as table %!eldsflight-seatsma!#

1-2-2 A "ubl!c constructor !s to be de%!ned and !$"le$ented !n the class# Th!s

constructor "ro!des all!nstance attr!butes !n the class w!th alues#

1-2-3 Dede%!ne the $ethod display_attributes o% the class lcl_airplane, so that,

us!n' the rede%!ned $ethod, the WDIT( state$ent d!s"la&s all!nstance

attr!butes#

1-3 @reate the subclass lcl_cargo_plane%or the class lcl_airplane# Also, create th!ssubclass !n &our !nclude "ro'ra$#

1-3-1 The class !s to hae a "r!ate !nstance attr!bute ma!_cargow!th the

sa$e t&"e as the table %!eldscplane-cargoma!#

1-3-2 A "ubl!c constructor !s to be de%!ned and !$"le$ented !n the class# Th!s

constructor "ro!des all!nstance attr!butes !n the class w!th alues#

1-3-3 Dede%!ne the $ethod display_attributes o% the class lcl_airplane, so that,

us!n' the rede%!ned $ethod, the WDIT( state$ent d!s"la&s all!nstance

attr!butes#

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2.#6 nheritance olutions

)nit* nheritance

To+ic* Creatin Class ierarchies

>--------------------------------------------------------------------->

> Re+ort #AP!"B;3_IN/#_AIN_a >

>--------------------------------------------------------------------->

> the cla''e' lcl_+a''enger_+lane and lcl_cargo_+lane are >

> in'tantiated$ Inheritance i' 'ho5n >

>--------------------------------------------------------------------->

REPORT 'a+?cB;3_inh'_main_a$

IN"LDE )icon,$

IN"LDE 'a+?cB;3_inh'_a$


r_arg te ref t ll_arg_lane6

r_aenger te ref t ll_aenger_lane6


#TART-O0-#ELE"TION$



C;$A$ E$C r_aenger $B+;&'

"m_name = DL? $;L&'D

"m_lanete = D9-900D

"m_eat = 79.

C;$A$ E$C r_arg $B+;&'

"m_name = D4S ?$ruleD "m_lanete = D9-00D

"m_arg = 77.

r_arg->"la_attr"5ute( ).

r_aenger->"la_attr"5ute( ).


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>--------------------------------------------------------------------->

> Include #AP!"B;3_IN/#_a >

>--------------------------------------------------------------------->

>------------------------------------------------------------------>


>------------------------------------------------------------------>

>$$$

>--------------------------------------------------------------------->

> "LA## lcl_cargo_+lane DE0INITION

>--------------------------------------------------------------------->

>

>--------------------------------------------------------------------->

CLASS ll_arg_lane #$%&'&&' &'?$;&&' %; ll_a"rlane.

+4L&C S$C&'.

----------------------

$?#S: ntrutr &+;&' "m_name +$ tr"ng

"m_lanete +$ alane-lanete

"m_arg +$ lane-argmax.

$?#S: "la_attr"5ute ;$#$%&'&&'.

+;&3A$ S$C&'.

----------------------

#AA: max_arg +$ lane-argmax.

$'#CLASS. ll_arg_lane #$%&'&&'

>--------------------------------------------------------------------->

> "LA## lcl_cargo_+lane IPLEENTATION

>--------------------------------------------------------------------->

>

>--------------------------------------------------------------------->

CLASS ll_arg_lane &+L$$'A&'.

$?# ntrutr. CALL $?# uer->ntrutr( "m_name = "m_name "m_lanete = "m_lanete ).

max_arg = "m_arg.

$'#$?#. ntrutr

$?# "la_attr"5ute.

uer->"la_attr"5ute( ).

M;&$: / Dax Carg = D6 max_arg.

4L&'$.

$'#$?#. "la_attr"5ute

$'#CLASS. ll_arg_lane &+L$$'A&'

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>--------------------------------------------------------------------->

> "LA## lcl_+a''enger_+lane DE0INITION

>--------------------------------------------------------------------->

>

>--------------------------------------------------------------------->

CLASS ll_aenger_lane #$%&'&&' &'?$;&&' %; ll_a"rlane..

+4L&C S$C&'.

$?#S: ntrutr &+;&' "m_name +$ tr"ng

"m_lanete +$ alane-lanete

"m_eat +$ fl"g!t-eatmax.

$?#S: "la_attr"5ute ;$#$%&'&&'.

+;&3A$ S$C&'.

#AA: max_eat +$ fl"g!t-eatmax.

$'#CLASS. ll_aenger_lane #$%&'&&'

>--------------------------------------------------------------------->

> "LA## lcl_+a''enger_+lane IPLEENTATION

>--------------------------------------------------------------------->

>

>--------------------------------------------------------------------->

CLASS ll_aenger_lane &+L$$'A&'.

$?# ntrutr.

CALL $?# uer->ntrutr( "m_name = "m_name "m_lanete = "m_

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