成果南大面試lecture1 2012

IntroductiontoJavaProgramming

Lecture1

IntroductiontoOOPandJava

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IntroductiontoJavaProgramming

Objectives

IntroductiontoOOP

Object-OrientedConcepts

Object-OrientedProgramming

JavaBasic

Javahistory&features

Javalanguage&platform

Javaprogram

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IntroductiontoJavaProgramming

Programs=Object/Class+…+Object/ClassObject/Class=Data/Operation

TypesofProgramming

ProceduralProgramming

Emphasisonproceduralabstraction

Top-downdesign,step-wiserefinement

Suitedforprogramminginthesmall

Programs=DataStructures+Algorithms

Object-orientedProgramming

Emphasisondataabstraction

Bottom-updesign,reusablelibraries

Suitedforprogramminginthelarge

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ObjectsandClasses:Example

Fielddefinitions

Fieldvalues

myCar:Car

colour=bluemodel=FiestafuelCapacity=45

Car

colour:Stringmodel:StringfuelCapacity:int

start():voidstop():void

move(direction:String):void

Car(colour:String,model:String,fuelCapacity:int)

<<instanceOf>>

start():voidstop():void

move(direction:String):void

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Classes&objects

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KindsofClassRelationships

Therearethreebasickindsofclassrelationships

Association

Aggregation(―partof‖)

Apetalispart-ofarose

Allowsonetoconstructnewclassesfromexistingone

Generalization(―kindof‖、“isa‖)

Aroseisakind-ofaflower

Generalizationprovidestheabilitytocreatesubclasses

Subclassessharethestructureoftheparentclass

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Association

“have”,“isrelatedto”,“isassociatedwith”...

Thisisthemostgeneraltypeofrelationship.

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“isdefinedbythe

collectionof”,...(wholeandpartscanexistseparately)

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Composition/Partitionvs.Aggregation

“ispartof”,“iscomposedof”,...(wholecannotexistwithouttheparts)

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Generalization

“isa”(IS-A),“akindof”(AKO)

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Inheritance

Theterm,inheritance,isusedinmanyobjectoriented(OO)programminglanguagestodescribethegeneralizationrelationship

Inheritanceisarelationshipwhereoneclasssharesthestructureorbehaviordefinedinoneclass(singleinheritance)ormore(multipleinheritance)

Theprocessofproducingnewclasseswithinheritedattributescreatesasuperclassandsubclasses

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Abstraction

Abstractionistheprocessofcapturingtheessentialwhilesuppressingthedetail

Withoutabstraction,theprogrammermustfaceanoverwhelminglevelofdetail

ProceduralAbstraction:top-downrefinement

DataAbstraction:Data+operation--class

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Encapsulation

Programminglanguagesenforceabstractionvia

encapsulation

Encapsulationisaninformationhidingmechanismthathidesdetailedinternalinformationaboutanabstraction

–Themechanicaldevicesofyourcarareencapsulated(hidden)bythechassisofthecar

AnADTforcesaseparationbetweenhowaclassofobjectsisusedandhowthatclassofobjectsisinternallyimplemented

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Polymorphism

Polymorphismmeans"havingmanyforms―,allowingobjectclassestoresponddifferently,dependingontheirtype

Methodswiththesamenamemaydodifferentthings,dependsontheobjectclasstheyareassociatedwith

PolymorphisminJava

Overloading

Overriding

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OOPandProceduralProgramming

Inproceduralprogramstheblocksarepiecesofcodewhichareexecutedastheprogramisrun

Inobject-orientedprogramsobjectshavelivesoftheirown–theycanbecreated,copied,destroyedorevenlost!

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WhatisJava?

Javaisaprogramminglanguage

generalpurpose

object-oriented

Javaisadevelopmentenvironment

JavaAPIs

Javaisanapplicationenvironment

JavaVirtualMachine

Javaisadeploymentenvironment

PlatformIndependence

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TheFeaturesofJavaLanguage

[SUN]TheJavaLanguage:

simple

object-oriented

network-savvy

interpreted

robust

Secure

architecture-neutral

high-performance

multithreaded

dynamiclanguage

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Simple

SyntaxisbasedontheC、C++

TheOOconceptsarethesameasSmalltalk

Nopointers

Garbagecollection

Small:40kb(run),125kb

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Object-oriented

JavaisahybridofpriorOOlanguages:

SimilaritiestoC++:

Syntax

Accesscontrol(public,private,protected)

SimilaritiestoSmalltalk:

Allbindingisdynamic

Everythingisanobject(well,almost)

SimilaritiestoAda:

Stronglytyped

Nomultipleinheritance

JavahasOOfeatures:

Inheritance,Encapsulation,Polymorphism

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Network-savvy

Distributeddata&distributedcomputing

TCP/IPLib

URL

Servlet

Usingthecoreclassesinmakesnetworkcomputingsimple

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Interpreted

ThecompliertranslatesJavasourcecodeintobytecode;theinterpreterprocessesbytecodewhenyourunaJavaprogram

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High-performance

Bytecode MachineCode

Compiler

JIT(JustinTime)Compiler

HotspotPerformanceEngine

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Robust

TheJavaplatformensuresthatprogramsruncorrectlyanddonotbreakwhentheunexpectedhappens

Stronglytyping

Lackofpointer

Garbagecollection

Exceptionhandling

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Secure

Lackofmemoryaccessdirectly

Bytecodeverification

Appletsinthesandbox

SecurityManager

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Architecture-neutralandPortable

Providesarchitectureneutralityinpartbyallowingnoimplementation-definedfeaturesbytecodeisportablebecauseitrunsonallimplementationsoftheJVM

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Multithreaded

Multithreadingcanbelooselydefinedasthesimultaneousexecutionofmultipleprocesseswithinaprogram

Javaisinherentlymulti-threaded

Forexample,multipleappletscanrunonthesamewebpagewitheachappletreceivingmoreorlessequalCPUtime

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Dynamic

Dynamicloadingclasses

Dynamicbinding

Dynamicsoftwaredevelopmentprocess

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OverviewOfTheJavaPlatform

TheJavaplatformincludes:

JavaVirtualMachine(JVM)

Anumberofpackagesthatsupportthecomplier,interpreter,andrun-timeenvironmentforJava(APIs)

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BriefHistoryofJava

1991:CreatedbyJamesGoslinget.al.atSunMicrosystems

"TheGreenTeam"–Calledthelanguage'Oak'

1994:BillJoy"HotJava"browser

1995:NetscapeagreestosupportJavainNetscapebrowsers

January1996:firstofficial

releaseJDK1.0

Web:applets,security,URL,networking

GUI:AbstractWindows

Toolkit(AWT)

…

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JDKVersions

JDK1.02(1995)

JDK1.1(1996)

majorchanges

Java2SDKv1.2(a.k.aJDK1.2,1998)

Java2SDKv1.3(a.k.aJDK1.3,2000)

Java2SDKv1.4(a.k.aJDK1.4,2002)

Java2SDKv1.5(a.k.aJDK1.5,2004)

Java2SDKv1.6(a.k.aJDK1.5,2006)

…

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Java2Architecture

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Java2(1)

J2SE(Java2StandardEdition)

BasicJavaspecificationfordesktopcomputerdevelopment

RunsintheJVM

J2EE(Java2EnterpriseEdition)

Multi-tier,highlyavailable,secure,reliableandscalable

RequiresdifferentJavaenterprisetechnologies

RunsintheJVM

J2ME(Java2MicroEdition)

set-topbox,JavaCard,etc….

RunsintheKVM

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JavaIDETools(1)

JavaDeveloper’sKits(JDK)

Compiler javac

InterpreterDebuggerAppletViewer

Generatorofheadfile

DocumentAdministrator

java

jdb

appletviewerjavahjavadoc

JavaarchivefileGenerator jar

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JavaIDETools(2)

Eclipse

InpriseJBuilder

MicrosoftVisualJ++

SymantecCafé

SunJavaWorkshop

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JDK&JRE

JDK:JavaDeveloper’sKits

Developer

JRE:JavaRuntimeEnviroment

User

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DifferencesBetweenJavaandC++

No―goto‖statement.

No(explicit)pointers!

Automaticgarbagecollection.

Nomultipleinheritance.

EverythinginJavaisdefinedwithinclasses.

Noheaderfiles!

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JavaPrograms

DifferentenvironmentsrequiredifferentkindsofJavaprograms:

Applications: canrunstandaloneonacomputerofanysize,andcanbeanythingfromlargesuitesofsoftwaretosimpleutilities

Applets: areprogramsthatcanbelaunchedfromHTML

documents（client-sidecodethatrunsinaWebbrowser)

—Servlets:runonJava-enabledWebserversandgenerateHTMLdocumentsthataresenttotheclientbrowserfordisplay（sever-sidecodethatrunsinaWebserver)

JavaBeans:areJavaclassesorgroupsofJavaclassesthatconformtoastrictsetofstandards(reusablecomponentsthatcanbemanipulateprogrammatically)

JavaMIDlet:arerunonthemobilephone

ASampleJavaApplicationProgram

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Applications(1)

foo.java

Javaprogram

sourcecode

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Applications(2)

foo.java

javac

Javacompiler

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Applications(3)

foo.java

javac

foo.class

Programbytecode

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Applications(4)

foo.java

javac

foo.class

java

Javabytecodeinterpreter

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Applets(1)

foo.java

javac

SameprocedureasforApplications

foo.class

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Applets(2)

foo.java

javac

foo.class

Netscape

Yourfavoritebrowser

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YourFirstJavaApplication(1)

/*Displayamessage*/publicclassHelloWorld{

publicstaticvoidmain(String[]args){

System.out.println("HelloWorld!");

}

}

HelloWorld.java

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YourFirstJavaApplication(2)

/*Displayamessage*/publicclassHelloWorld{

publicstaticvoidmain(String[]args){

System.out.println("HelloWorld!");

}

}

Thiswillbethe

nameoftheresulting.classfile

HelloWorld.java

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YourFirstJavaApplication(3)

C:\>javacHelloWorld.javaC:\>javaHelloWorld

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YourFirstJavaApplication(4)

C:\>javacHelloWorld.javaC:\>javaHelloWorld

Thisproduces

HelloWorld.class

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YourFirstJavaApplication(5)

C:\>javacHelloWorld.java

C:\>javaHelloWorld

ThisrunsHelloWorld.class

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YourFirstJavaApplet(1)

importjava.applet.Applet;importjava.awt.Graphics;

publicclasshelloXextendsApplet{publicvoidpaint(Graphicsg){

g.drawString("Helloworld!",50,25);

}

}

helloX.java

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YourFirstJavaApplet(2)

C:\>javachelloX.java

Thisproduceshello.class(likebefore)

butthen...

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YourFirstJavaApplet(3)

<HTML>

<HEAD>

<TITLE>