1. introduction based on java software development, 5 th ed. by lewis &loftus

1. Introduction1. Introduction

Based on Based on Java Software Development, 5Java Software Development, 5thth Ed. Ed.

By Lewis &LoftusBy Lewis &Loftus

TopicsTopics

Java Programming Language Java Programming Language OverviewOverview

Program DevelopmentProgram Development Object-oriented Programming Object-oriented Programming

OverviewOverview

Java CharacteristicsJava Characteristics Object-oriented LanguageObject-oriented Language

Program consists of a collection of Program consists of a collection of classesclasses Each class contains Each class contains

one or more one or more attributes—data one or more one or more methodsmethods—program —program

statementsstatements Syntax is like C++.Syntax is like C++.

But it is very different from C++ But it is very different from C++ Primitive types have standard sizesPrimitive types have standard sizes Automatic garbage collectionAutomatic garbage collection No pointersNo pointers

Benefits of JavaBenefits of Java PortablePortable

The same source code can be compiled and The same source code can be compiled and executed on any Operating System executed on any Operating System

SecureSecure Designed from the start with security in mind Designed from the start with security in mind

Designed for Network ProgrammingDesigned for Network Programming Makes network-related programming easy Makes network-related programming easy "Network is the computer"--Sun's company motto"Network is the computer"--Sun's company motto

Dynamic ProgramDynamic Program A program can load various modules as needed A program can load various modules as needed

during execution. during execution. InternationalInternational

Java was developed from the start with Java was developed from the start with international use in mind. E.g., Unicode (16 bits) international use in mind. E.g., Unicode (16 bits) encodingencoding

Running a Java ProgramRunning a Java Program

Source Code Bytecode Output

Text Editor Compiler JVM

To Run a Java ProgramTo Run a Java Program

Suppose source code Suppose source code MyProgram.javaMyProgram.java exists in C:\310\.exists in C:\310\.

Compile the source code to Compile the source code to bytecode, which will be named as bytecode, which will be named as MyProgram.classMyProgram.classC:\310> C:\310> javac MyProgram.javajavac MyProgram.java

Run (interpret) the bytecode.Run (interpret) the bytecode.C:\310> C:\310> java MyProgramjava MyProgram

Java Program StructureJava Program Structure

// This is a comment line

class MySample {

}

Class body

Class header

Java Program Structure Java Program Structure (cont.)(cont.)

// This is a comment line

class MySample { public static void main(String args[]) {

}}

Method bodyMethod header

Java Program Structure Java Program Structure (E.g.)(E.g.)

// This is a sample program

class Welcome { // prints a greeting in two lines public static void main(String[] args) { System.out.println(“Hello, Hawaii.”); System.out.println(“Welcome to Kaimuki.”); }

}

RandomTest.javaRandomTest.java// This program generates 10 random numbers.

import java.util.Random;

public class RandomTest { public static void main(String[] args) { Random rand = new Random();

for (int n = 1; n <= 10; n++) { System.out.println(n + ". " + rand.nextFloat ()); } }}

Countdown.javaCountdown.java

// This program counts down numbers from// 10 to 0.

class Countdown { public static void main(String[] args) { for (int i = 10; i >=0; i--) { System.out.println(i + "!"); } System.out.println("Lift Off!"); }}

CommentsComments

Comments do not affect how a Comments do not affect how a program worksprogram works

Java comments can take three forms:Java comments can take three forms:

// This comment runs to end of line.// This comment runs to end of line.

/* This form can be for one line *//* This form can be for one line *//* or it can cover /* or it can cover several lines */ several lines */

/** This is javadoc comment *//** This is javadoc comment */

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IdentifiersIdentifiers

IdentifiersIdentifiers are the names used in a are the names used in a programprogram

Can be made up of letters, digits, the Can be made up of letters, digits, the underscore character ( _ ), and the underscore character ( _ ), and the dollar signdollar sign

Cannot begin with a digitCannot begin with a digit

Java is Java is case sensitivecase sensitive - - TotalTotal, , totaltotal, , andand TOTALTOTAL are different are different identifiersidentifiers

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Identifiers (cont.)Identifiers (cont.)

Java convention:Java convention: Lower case for variables: Lower case for variables: name, totalname, total

Upper case for constants: Upper case for constants: MAXIMUMMAXIMUM

Mixed for compound words: Mixed for compound words: lastDayOfWeeklastDayOfWeek

Reserved words (53 in Java) Reserved words (53 in Java) may not be may not be used as identifiers.used as identifiers.

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Reserved WordsReserved Words

The Java reserved words:The Java reserved words:abstractassertbooleanbreakbytecasecatchcharclassconstcontinuedefaultdodouble

elseenumextendsfalsefinalfinallyfloatforgotoifimplementsimportinstanceofint

interfacelongnativenewnullpackageprivateprotectedpublicreturnshortstaticstrictfpsuper

switchsynchronizedthisthrowthrowstransienttruetryvoidvolatilewhile

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White SpaceWhite Space Whte spaces:Whte spaces:

spaces, line breaks, and tabs spaces, line breaks, and tabs

used to separate words and symbols in a used to separate words and symbols in a programprogram

Extra white space is ignoredExtra white space is ignored

Enhance program readability with: Enhance program readability with: Blank line to separate major section Blank line to separate major section

Indentation for loop bodyIndentation for loop body

Indentation in If statementsIndentation in If statements

OutlineOutline



OverviewOverview

Programming Language Programming Language LevelsLevels

Machine languageMachine language 0011 1100 1010 1111 1011 0011 1011 1101 11100011 1100 1010 1111 1011 0011 1011 1101 1110

0101 1010 1001 0011 1000 1001 0011 1000 00100101 1010 1001 0011 1000 1001 0011 1000 00100001 1101 0010 0111 1010 1011 0111 1100 01100001 1101 0010 0111 1010 1011 0111 1100 0110

Assembly languageAssembly language ori $8,$0,0x2 ori $8,$0,0x2

ori $9,$0,0x3 ori $9,$0,0x3 addu $10,$8,$9 addu $10,$8,$9

High-level languageHigh-level language sum = num1 + num2sum = num1 + num2

Fourth-generation languageFourth-generation language Report generatorsReport generators

Form generatorsForm generators

Increasing abstraction

Program DevelopmentProgram Development

Steps in Program DevelopmentSteps in Program Development

Writing source codeWriting source code

Compiling source code into machine—Compiling source code into machine—readable formreadable form

Debugging and Testing programDebugging and Testing program

Executing programExecuting program

Typical Programming Typical Programming ProcessProcess

Write Source code in high-level language—Write Source code in high-level language—e.g., Javae.g., Java

Translate source code into machine Translate source code into machine languagelanguage CompilerCompiler translates the entire source code translates the entire source code

into single machine programinto single machine program InterpreterInterpreter translatestranslates and executesand executes the the

source code one line at a time.)source code one line at a time.)

Checking for errors and correcting themChecking for errors and correcting them Execute programExecute program

Each type of CPU requires machine code Each type of CPU requires machine code specific to it (using operating system)specific to it (using operating system)

Basic Program Basic Program DevelopmentDevelopment

errors

errors

Edit andsave program

Compile program

Execute program andevaluate results

©2007 Pearson Addison Wesley

Java Programming Java Programming ProcessProcess

Write source code in JavaWrite source code in Java Translate source code into a Translate source code into a

bytecodebytecode (machine laguage). (machine laguage). Execute the bytecode by interpretor Execute the bytecode by interpretor

(Java Virtual Machine)(Java Virtual Machine) Each CPU runs the Virtual MachineEach CPU runs the Virtual Machine Which executes the bytecodeWhich executes the bytecode

Java EnvironmentJava Environment

The Java environment consists of the The Java environment consists of the following elements.following elements.

Java Programming Language Java Programming Language grammar for writing application programs, grammar for writing application programs,

applets, JavaBeans components, etc.applets, JavaBeans components, etc. Java Virtual Machine (JVM) Java Virtual Machine (JVM)

software for executing Java binary programs, software for executing Java binary programs, called byte codecalled byte code

Java Platform (Java Standard Library, Java Java Platform (Java Standard Library, Java API) API) set of predefined classesset of predefined classes

Java Virtual MachineJava Virtual Machine Source code is compiled into a binary file Source code is compiled into a binary file

known as a bytecode. known as a bytecode. Bytecode is then interpreted by the Bytecode is then interpreted by the Java Java

Virtual MachineVirtual Machine, which sits atop an , which sits atop an operating system--Windows, MacOS, operating system--Windows, MacOS, Lunux. Lunux.

Since the bytecode does not need to know Since the bytecode does not need to know the kind of OS on which it is being the kind of OS on which it is being executed--the JVM is tailored to particular executed--the JVM is tailored to particular OS--a Java code is highly portable from OS--a Java code is highly portable from one type of computer system to another.one type of computer system to another.

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Java TranslationJava Translation

Java sourcecode

Machinecode

Javabytecode

Bytecodeinterpreter

Bytecodecompiler

Javacompiler


TerminologyTerminology SyntaxSyntax

Rules of language (grammar)Rules of language (grammar) d = a(b + c); -- syntax errord = a(b + c); -- syntax error

SemanticsSemantics Meaning of the languageMeaning of the language speed = distance * time;speed = distance * time;

--syntactically correct, semantically wrong--syntactically correct, semantically wrong ErrorsErrors

Compile-time error (e.g., syntax error)Compile-time error (e.g., syntax error) Run-time error (e.g., dividing by 0)Run-time error (e.g., dividing by 0) Logic error (program runs, but produces wrong Logic error (program runs, but produces wrong

result)result)

OutlineOutline



OverviewOverview

Problem SolvingProblem Solving

Steps in problem solving:Steps in problem solving:

Understand the problemUnderstand the problem Design a solutionDesign a solution Consider alternatives and refine the solutionConsider alternatives and refine the solution Implement the solutionImplement the solution Test the solutionTest the solution

These steps are not linear—they overlap These steps are not linear—they overlap and repeatand repeat

Problem Solving (cont.)Problem Solving (cont.)

The key strategy to solve a complex The key strategy to solve a complex problem is to break it down into problem is to break it down into manageable pieces and solve each manageable pieces and solve each piece—piece—dividedivide and conquerand conquer method. method.

Object-orientedObject-oriented approach sees a approach sees a program in terms of a collection of program in terms of a collection of “objects” interacting with each other.“objects” interacting with each other.

With Java, objects and classes are the With Java, objects and classes are the basic units of a programbasic units of a program

Objects and ClassesObjects and Classes

An OO program consists of a collection of An OO program consists of a collection of objects interacting with each other.objects interacting with each other.

Suppose you are writing a game program Suppose you are writing a game program that involves several dogs, cats, and cars. that involves several dogs, cats, and cars. (Use your imagination.)(Use your imagination.)

Here are some dog objects: Here are some dog objects: Fido—a big brown bulldogFido—a big brown bulldog Lassie—a tall collieLassie—a tall collie Taro—a small, white akitaTaro—a small, white akita

ObjectsObjects

Attributes: name = Fido breed = bulldog color = brown weight = 30 kg height = 50 cmOperations: bark() display()

Attributes: name = Lassie breed = collie color = brow weight = 25 kg height = 70 cmOperations bark() display()

Attributes: name = Taro breed = akita color = white weight = 10kg height = 30 cmOperations bark() display()

Dog1

Dog2Dog3

ClassClass A class is an A class is an abstractionabstraction of the objects of of the objects of

the same type. Fido, Lassie, and Taro are the same type. Fido, Lassie, and Taro are all all instancesinstances of the of the DogDog class. class.

Each objects has a number of Each objects has a number of attributesattributes (with different values) and (with different values) and operationsoperations (same methods). (same methods).

A class is A class is a template for creating (specifying) objects of a a template for creating (specifying) objects of a

particular type.particular type. like blueprint for creating objects of a like blueprint for creating objects of a

particular typeparticular type

Class (cont.)Class (cont.)

A class is composed ofA class is composed of Class NameClass Name AttributesAttributes Operations (methods)Operations (methods)

Once a class is defined, objects can Once a class is defined, objects can be created (instantiated) from it.be created (instantiated) from it.

Class DiagramClass Diagram

Dog

breedcolorweightheight

Bark()display()

Class name

Attributes

Operations

Car

makeengineSizecolormaxSpeed

Start()accelerate()stop()display()

Class (summary)Class (summary) A class defines an object.A class defines an object.

A class is the blueprint, or template, of an objectA class is the blueprint, or template, of an object

A class represents a concept, and an object A class represents a concept, and an object represents the embodiment of that conceptrepresents the embodiment of that concept

Multiple objects can be created from the same Multiple objects can be created from the same classclass

The class uses methods to define the behaviors of The class uses methods to define the behaviors of the objectthe object

The class that contains the The class that contains the mainmain method of a Java method of a Java program represents the entire programprogram represents the entire program

Classe and ObjectClasse and Object

Bank Account

A class(the concept)

John’s Bank AccountBalance: $5,257

An object(the realization)

Bill’s Bank AccountBalance: $1,245,069

Mary’s Bank AccountBalance: $16,833

Multiple objectsfrom the same class


InheritanceInheritance One class can be used to derive another via One class can be used to derive another via

inheritanceinheritance

Classes can be organized into hierarchiesClasses can be organized into hierarchies

Bank Account

Account

Charge Account

Savings Account

Checking Account


Inheritance (2)Inheritance (2) One class can be used to derive another via One class can be used to derive another via

inheritanceinheritance

Classes can be organized into hierarchiesClasses can be organized into hierarchies

Full-time

Employee

Part-time ]

Hourly-wage

Annual-salary


PracticePractice

Specify some relevant attributes and Specify some relevant attributes and operations for the following classes.operations for the following classes. Bank AccountBank Account BookBook Browser windowBrowser window Circle (geometric figure)Circle (geometric figure) Rectangle (geometric figure)Rectangle (geometric figure)

1. introduction based on java software development, 5 th ed. by lewis &loftus

Documents

java convention

import java

java software development

program worksjava comments

class countdown

comment lineclass mysample

compound words

lastdayofweekreserved