tipuri de date in java.pdf

7/25/2019 Tipuri de date in Java.pdf

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Structuri de Date n JAVA (II)

Programarea orientat obiect n JavaClas. Variabile membre. Crearea obiectelor

i!uri !rimitive. Constructori. "etodeControlul e#ecu$ieiVectori. Probleme la utili%area obiectelorPac&ete. 'eglementarea accesuluiVariabile. 'eerin$eVariabile membre statice. "etode staticeDomeniu de e#isten$


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Programarea *rientat *biect

*biectele au stare o !ersoan este un obiect caracteri%at de

nume+ v,rst+ C-P Programatorii c&eam metodele obiectelor!entru a reali%a calcule i a modiica aceaststare

!rogramator/ ce v,rst ai0 obiect/ am !rogramator/ a%i e %iua ta obiect/ atunci mi incremente% v,rsta cu 1


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2

3n !rogram JAVA

packagehello;

importjava.util.System;

classHelloWorld{

StringmyString;

voidshout() {

myString = newString(Hello world);

System.out.println (myString);}

publicstaticvoidmain(String! args) {

HelloWorldmyHelloWorld= newHelloWorld();

myHello"orld.shout ();}

}


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Clas

5ablon !entru generarea obiectelorJava e un limba6 orientat obiect+ deci orice este oclas

classHelloWorld7 88 numele clasei

... 9deini$ii de metode i variabile membre: ...

;


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;

9ti!ul clasei: 9numele variabilei:>


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Crearea obiectelor

Humanbob@ newHuman()>

Crearea obiectelor se ace cu o!eratorul newB*biectul @ instan$ a claseibobeste o reerin$ la obiect (adres)

Se asigneazobiectul construit variabilei bob

9ti!: 9nume variabil: @ 9obiect nou:>


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De ce nu a trebuit s scriem

bob.age @ ne int ()> 00


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E

i!uri !rimitive

-u oriceeste un obiect3nele lucruri sunt !rea sim!le i !rea recventutili%ate ca s le considerm obiecte/

boolean+ s&ort+ bFte+ int+ long+ double+ loat+c&ar


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G

Clase ra!!er

i!urile !rimitive nu sunt clase derivate din clasa *b6ectPentru a le trata similar cu obiectele le asociem claseClasa asociat unui ti! !rimitiv se numete clas wrapper

Constructor Accesor method

Byte public Byte(byte value) public byte byteValue ()

Short public Short(short value) public short shortValue()

Integer public Integer(int value) public int intValue ()

Long public Long(long value) public long longValue ()Float public Float(float value) public float floatValue ()

Double public Double(double value) public double doubleValue ()

Character public Character(char value) public char charValue ()

Boolean public Boolean (boolean value) public boolean booleanValue ()

Wrapperclass


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1H

olosirea claselor ra!!er

inti @ 4>int6>

Integer e#am!le @ newInteger (i)> 88 e#am!le co!ia%a valoarea 46 @ e#am!le.intValue ()> 88 6 este acum 4

Integer a @ >Integer b @ 1>Integer c @ a b> 88 este o absurditate>

88 KK nu se !oate olosiint r @ a.intValue () b.intValue ()>Integer d @ newInteger (r)> 88 varianta corect


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11

Variabila membr myString

packagehello;

importjava.util.System;

classHelloWorld{

StringmyString;

voidshout() {

myString = newString(Hello world);

System.out.println (myString);}

publicstaticvoidmain(String! args) {

HelloWorldmyHelloWorld= newHelloWorld();

myHello"orld.shout ();}

}


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1

"etode

Procesea% starea obiectului

9ti! returnat: 9numele metodei: ( 9!arametri: ) 79cor!ul metodei:

;

mF=elloLorld.s&out ()>88 se olosete K.K !entru a accesa metoda


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Constructori

Constructorii sunt metode s!eciale

nu au ti! returnat se olosesc !entru a ini$iali%a variabilele

membre!rimesc !arametri+ au cor! al metodei+ dar nu

au return


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Cor!ul metodei

Stringfirstname(Stringullname) 7ints!ace @ ullname.inde#* ( )>

Stringord @ ullname.substring (H+ s!ace)>returnord>

;

oric,$i !arametrideclar variabile localereturnea% un singur lucru (void @ nu ntorc nimic)


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1 88 variabila c are valoarea null...

c @ newCutie()> 88 deMabia aici sMa creat obiectul

oate variabilele declarate au im!licit valoarea H'eerin$ele se ini$iali%ea% tot cu H (null)Dac olosim o reerin$ neMcreeat nc se vaarunca o e#ce!$ie NullPointerException


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1?

Cutie a;Cutie b;

a = new Cutie ();a.deschide ();

b = a;

b.deschide ();

nullCutie a Cutie b null

Cutie a Cutie b null

Cutie a Cutie b

Cutie a Cutie b


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1

Controlul e#ecu$iei

if(bob.age 9 1) 7 if(!redicat) 788 nu eectuea% ...

; elseif(bob.&asCard ()) 7 ; elseif(!redicat) 788 altceva ...; else7 ; elseif(!redicat2) 7

88 n rest ...

; ; else if(!redicat-) 7...

; else7 ... ;


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1E

Predicate

Predicatele se evaluea% ie la trueie la false(boolean)

9+ :+ @@+ 9@+ :@+

bo#.isNm!tF ()

bo#.numberOoos () @@ H(bo#.numberOoo () : 1)bo#.numberOoos () @ "AQR-3"ON'RO**S


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1G

Oucla or

for(inti @ H > i 9 2 > i ) 7SFstem.out.!rintln (i)> 88 ti!rete H 1

;

for(9ini$iali%are: > 9!redicat: > 9incrementare: ) 7se e#ecut de iecare dat

o singur dat*!rirea se ace n momentul c,nd !redicatul devinealse.


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H

Oucla &ile

inti @ H>while(i 9 2) 7

SFstem.out.!rintln (i)>i @ i 1>;

while(9!redicat:) 7...;


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1

Combinarea !redicatelor

TT este 5I logicUU este SA3 logic

a. bob.age :@ 1 TT bob.&asCard ()

b. someone.name.euals(OobB)c. (true UU alse) TT true


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Vectori

Vectorii sunt tot obiecte+ dar s!eciale+ !recumti!urile !rimitive

StringWX !ets @ newStringWX>!etsWHX @ newString(luFB)>!etsW1X @ S!otB> 88 irul e#ist de6a

StringWX !ets @ newStringWX 7luFB+ S!otB;>SFstem.out.!rintln (!ets.lengt&)> 88 aiea%


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2

C,te ti!uri avem 0

Primitive int a @ 2

*biecte Integer a @ ne Integer (2)> Integer sum @ a.add ( Vectori


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*biectele !ot cau%a !robleme

!etsW2X :: !rogramul se o!rete+ se arunce#ce!$ia ArraF*ut*Oounds

StringWX str>str.lengt& :: o!rire+ arunc -ullPointerN#ce!tion

Integer a @ ne Integer (2)> 88 a !rimete 2a.add ( 88 a rm,ne 2a @ a.add ( 88 a !rimete E


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!ublic void !lantOean () 7

!lanted @ true>;

!ublic static void main (StringWX args) 7Oean bean @ ne Oean ()>

bean.!lantOean ()> // invocat la instan;

;


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2?

"etode statice

!ublic class Oean 7!rivate boolean !lanted @ alse>!ublic staticvoid !lantOean (Bean bean) 7

bean.!lanted @ true>;

!ublic static void main (StringWX args) 7Oean bean @ ne Oean ()>

Bean.!lantOean (bean)> // invocat la clas// bean.plantBean (bean!" e permis #ar nerecoman#at$;

;


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2

'eerin$e

oate obiectele trimise ca !arametri ctre ometod sunt trimise ca reerin$e

'eerin$ele au un domeniu de e#isten$ (sco!e)Domeniul se deinete cu acoladele 7 i ;'eerin$ele e#ist de la declararea lor i !,n la

terminarea domeniului (acolad nc&is)Variabilele membre !ot i reerite n toat clasaParametrii !ot i reeri$i n toat metoda


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2E

N#em!lu de domenii

!ublic class Sco!eN#am!le 7!rivate int globalield>

!ublic int met&od (int !arameter) 7int localVar1>i (globalield : H) 7

int #>;int localVar>

;;


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2G

3n alt e#em!lu de domenii

!ublic class Sco!eN#am!le 7!rivate int globalield>

!ublic int met&od (int !arameter) 7int globalield> // posibil% #ar se pier#e vizibilitatea$int localVar>i (this.globalield : H) 7// accesarea variabilei membre

int #>

;int localVar> // #eclaraie ilegal& acelai #omeni'$;

;


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4H

Preci%ia loating !oint

SFstem.out.!rintln (1.HH M .4)>88 H.?1HHHHHHHHHHHHHHHH1

SFstem.out.!rintln (1.HH Y G [ .1H)>88 H.HGGGGGGGGGGGGGGGGG

tipuri de date in java.pdf

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