OOP Class 2

CS445 - Object Oriented Design and Programming

An Object of

c

lass Time

OPERATIONS DATA

Set Increment Write .

.

.

Time Private data: hrs 8 mins 25 secs 42 CS445 - Object Oriented Design and Programming

Definitions

CS445 - Object Oriented Design and Programming

Definitions

  Definitions of object on the Web: a tangible and visible entity; an entity that can cast a shadow; "it was full of rackets, balls and other objects"   Definitions of object-oriented on the Web “object-oriented ... techniques where data carries with itself the "methods" (also known as "functions") used to handle that data. An OO programmer, for instance, can write a statement such as "

object.print()"

procedural code…” without having to be concerned about what kind of object will be involved at "run time" or what its printing method is. Object-oriented code is both more flexible and more organized, so it is far easier to write, read, and change than www.3dartist.com/WP/dempy/help/glossary.htm

 “… A style of software development and packaging based on how real world objects relate to one another. Data and procedures are combined in objects; objects communicate with each other via messages; similar objects are grouped together into classes; data and procedures are inherited through a class hierarchy…” www.olenick.com/html/glossary.html

CS445 - Object Oriented Design and Programming

Definitions

 Definitions of object-oriented design on the Web:  entails transforming the analysis model into a feasible design. kaykeys.net/science/computerwork/oodesign/  A software design method that models the characteristics of abstract or real objects using classes and objects. software.allindiansite.com/java/ojava.html

  Object-oriented design (OOD) is a design method in which a system is modeled as a collection of cooperating objects and individual objects are treated as instances of a class within a class hierarchy. en.wikipedia.org/wiki/Object-oriented_design

CS445 - Object Oriented Design and Programming

 

Definitions of object-oriented analysis on the Web:

Object-oriented analysis

– builds a model of a system that is composed of objects. The behavior of the system is achieved through collaboration between these objects, and the state of the system is the combined state of all the objects in it. Collaboration between objects involves them sending messages to each other. Definitions of object-oriented programming on the Web: – “… A programming approach based on the concepts of data abstraction and inheritance. Unlike procedural programming techniques, …” – “… Style of programming characterized by the use of separate "objects" to perform different tasks within a program. These "objects" usually consist of an abstract data type or class, along with the methods used to manipulate that abstract data type …” – “… A programming methodology built around objects and based on sending messages back and forth between those objects. The basic concepts of object-oriented programming are encapsulation, inheritance, and polymorphism …”

CS445 - Object Oriented Design and Programming

Modeling the Real World

  Components of a software system is an interpretation of the real world – Model , a representation of parts of the real world – Algorithm, capture the computation needed to manipulate the model Object Orientation is a software development model that makes use of objects as a representation of the real world – An object represents anything in the real world that can be distinctly identified.

– A class represents a set of objects with similar characteristics and behavior

CS445 - Object Oriented Design and Programming

50’s – 60’s 70’s – 80’s

History

Focus  Algorithm –solving computation problems and –researching efficient algorithms Data complexity Model Used Computation- Oriented Control Flow Data-Oriented Data Flow OO Balanced view of data and computation OO models made of objects which contain data and algorithms

CS445 - Object Oriented Design and Programming

Module Structure Chart

Main Prepare File for Reading Get Data Print Data Find Weighted Average Print Weighted Average Print Heading CS445 - Object Oriented Design and Programming

Two Design Strategies

FUNCTIONAL DECOMPOSITION FUNCTION OBJECT-ORIENTED DESIGN OBJECT FUNCTION . .

.

OBJECT FUNCTION .

.

. CS445 - Object Oriented Design and Programming .

.

. OBJECT

Software Process Models

CS445 - Object Oriented Design and Programming

Unified Process

   a “use-case driven, architecture-centric, iterative and incremental” software process closely aligned with the Unified Modeling Language (UML) Tools are used to describe customer views (use cases) Used mainly for OO based methodologies  Runs in phases

CS445 - Object Oriented Design and Programming

The Unified Process (UP)

Phase 1 Communication + Planning Phase 2 Planning + Modeling result

Release soft ware increment

pr o duct io n inception CS445 - Object Oriented Design and Programming Phase 3 Coding, unit test & integrate Components co nst r uct ion t r ansit ion Phase 4 Deployment

UP Phases

UP Phases

Incept ion Elaborat ion Const ruct ion Transit ion

Workflows

Requirements Analysis Design Implementation Test Support

Iterations

#1 #2 #n-1 #n Product ion

CS445 - Object Oriented Design and Programming

Incept ion phase Vision document Init ial use-case model Init ial project glossary Init ial business case Init ial risk assessment . Project plan, phases and it erat ions. Business model, if necessary . One or more prot ot y pes

I n c e p t i o n

UP Work Products

Elaborat ion phase Const ruct ion phase Use-case model Supplement ary requirement s including non-funct ional Analy sis model Soft ware archit ect ure Descript ion. Execut able archit ect ural prot ot y pe. Preliminary design model Rev ised risk list Project plan including it erat ion plan adapt ed workflows milest ones t echnical work product s Preliminary user manual Design model Soft ware component s Int egrat ed soft ware increment Test plan and procedure Test cases Support document at ion user manuals inst allat ion manuals descript ion of current increment Transit ion phase Deliv ered soft ware increment Bet a t est report s General user feedback

CS445 - Object Oriented Design and Programming

Agile Development

CS445 - Object Oriented Design and Programming

The Manifesto for Agile Software Development

“We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value:

•

Individuals and interactions over processes and tools

•

Working software over comprehensive documentation

•

Customer collaboration over contract negotiation

•

Responding to change over following a plan That is, while there is value in the items on the right, we value the items on the left more.”

Kent Beck et al

CS445 - Object Oriented Design and Programming

What is “Agility”?

 Effective (rapid and adaptive) response to change  Effective communication among all stakeholders   Organizing a team so that it is in control of the work performed

Yielding …

 Drawing the customer onto the team Rapid, incremental delivery of software

CS445 - Object Oriented Design and Programming

An Agile Process

     Is driven by customer descriptions of what is required (scenarios) Recognizes that plans are short-lived Develops software iteratively with a heavy emphasis on construction activities Delivers multiple ‘software increments’ Adapts as changes occur

CS445 - Object Oriented Design and Programming

Extreme Programming (XP)

  The most widely used agile process, originally proposed by Kent Beck XP Planning – Begins with the creation of “ user stories ” – Agile team assesses each story and assigns a cost – Stories are grouped to for a deliverable increment – A commitment is made on delivery date – After the first increment “ project velocity ” is used to help define subsequent delivery dates for other increments

CS445 - Object Oriented Design and Programming

Extreme Programming (XP)

   XP Design – Follows the KIS principle – Encourage the use of

CRC

cards (see Chapter 8) – For difficult design problems, suggests the creation of “ spike solutions ”— a design prototype – Encourages “ refactoring ”—an iterative refinement of the internal program design XP Coding – Recommends the construction of a unit test commences – Encourages “ pair programming ” for a store

before

coding XP Testing – All unit tests are executed daily – “Acceptance tests” are defined by the customer and executed to assess customer visible functionality

CS445 - Object Oriented Design and Programming

Extreme Programming (XP)

spike solut ions simple design

prot ot ypes CRC cards

user st ories

values accept ance t est crit eria

it erat ion plan ref act oring Release sof t ware increment

project velocit y comput ed

unit t est cont inuous int egrat ion accept ance t est ing

CS445 - Object Oriented Design and Programming

pair programming

OO Design & Programming Java Basics

CS445 - Object Oriented Design and Programming

   

Classes and Objects

Class Point {

An object:

Int x, y;

Attributes or fields: point1

Public void move (intd dx, int dy) { x +=dx; y +=dy;

int x, y;

}

A method:

}

void move(int dx, int dy) A message: point1.move(10, 10)

CS445 - Object Oriented Design and Programming

An Object of

c

lass Time

OPERATIONS DATA

Set Increment Write .

.

.

Time Private data: hrs 8 mins 25 secs 42

Modularity Abstraction Encapsulation Inheritance Polymorphism Message Passing

CS445 - Object Oriented Design and Programming

Developing a Java Application

1.

2.

3.

• • • Write the source code Using an Integrated Development Environment (IDE) or text editor Save in a

.java

file Compile the source code:

javac ClassName.java

Creates

.class

file • Execute the application:

java ClassName

Run by the Java Virtual Machine (JVM)

CS445 - Object Oriented Design and Programming

A First Application

1 // First program in Java 2 // FirstProgram.java

3 4 public class

FirstProgram

5 { 6 public static void

main

( String [] args ) 7 { 8 System.out.println( "Programming is not " 9 + " a spectator sport!" ); 10 System.exit( 0 ); 11 12 } }

CS445 - Object Oriented Design and Programming

  Class:

FirstProgram

Method:

main

(...)  Statement: System.out.println(...)  Comments: – // a comment – /* another comment */  Source file:

FirstProgram

.java

CS445 - Object Oriented Design and Programming

  

Program Errors

Compiler errors – Found by the compiler. – Usually caused by incorrect syntax or spelling Run-time errors – Reported by the JVM – Usually caused by incorrect use of prewritten classes or invalid data Logic errors – Found by testing the program – Incorrect program design or incorrect execution of the design

CS445 - Object Oriented Design and Programming

Edit Think

Program Life Cycle

Source Program Compile Link Load Execute Library routines Other object files

CS445 - Object Oriented Design and Programming

Introduction: Java Platform

 Java TM platform is based on the idea that the same software should run on many different kinds of computers, consumer gadgets, and other devices.  Portability – Java platform allows you to run the same Java application on lots of different kinds of computers.

CS445 - Object Oriented Design and Programming

JVM



Java virtual machine or "JVM

TM

” – a translator that turns general Java platform instructions into tailored commands that make the devices do their work

CS445 - Object Oriented Design and Programming

Java Program Phases

1.

2.

3.

4.

5.

– Edit IDE, vi, emacs, notepad – Compile javac – Load Class Loader – Verify Verifier (Security and Validation) – Execute Java Interpreter (java or appletviewer)

CS445 - Object Oriented Design and Programming

The java Compiler

 javac – Creates bytecodes – Stored on disk as .class

– Each file contains bytecode for one and only one class

CS445 - Object Oriented Design and Programming

The java Class Loader



Loads bytecodes in memory – Loads .class

files from disk into memory

CS445 - Object Oriented Design and Programming

The java Bytecode Verifier

 Confirms that all bytecodes are: – Valid and – Don't violate Java’s Security restrictions  Works on bytecodes from memory

CS445 - Object Oriented Design and Programming

The java Interpreter

  Reads bytecodes and translate them into a language that is relevant to the targeted computer architecture – PC – Machintosh – Cell Phone For applets execution its built into the browser or the appletviewer

CS445 - Object Oriented Design and Programming

Your first program:

HelloWorldApp

.java

  

Displays the greeting "Hello world!". To create this program, you will: Create a source file

–

A source file contains text, written in Java. Compile the source file into a bytecode file .

–

The compiler,

javac

, converts these instructions into a bytecode file CS445 - Object Oriented Design and Programming

Your first program:

HelloWorldApp



Run the program contained in the bytecode file

– –

The Java interpreter implements the Java VM This interpreter takes your bytecode file and carries out the instructions by translating them into instructions that your computer can understand.

CS445 - Object Oriented Design and Programming

JRE

CS445 - Object Oriented Design and Programming

JAVA Program

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

System.out.println("Hello World");

} }

CS445 - Object Oriented Design and Programming

Steps

1.

2.

3.

Save the file as

HellowWordApp.java

–

Compile

Javac HellowWordApp.

java  HellowWordApp.

class –

Run the program

Java HellowWordApp

CS445 - Object Oriented Design and Programming

Output

CS445 - Object Oriented Design and Programming

What Can be a Class?

      Physical Objects – equipments, devices, products People – Students, Faculty, Customers Organizations – Universities, Companies, Departments, Bank Places – Buildings, Rooms, Seats Events – Mouse click, order request, purchase orders Concepts – Transaction  The domain determines the classes

CS445 - Object Oriented Design and Programming

What Features Should a Class Have?

  Actions should be modeled as methods of a class Verb phrases    Underline the verbs and nouns in the description of the requirements and use cases Nouns are candidate classes or attributes Verbs are candidate methods

CS445 - Object Oriented Design and Programming

Java Programming Language

 Java Basics  OO Basics  UML Basics

CS445 - Object Oriented Design and Programming

Data Types, Variables, and Constants

       We use Symbolic Names to refer to data We must assign a data type for very identifier (symbolic name) Declaring Variables Primitive Data Types Initial Values and Literals String Literals and Escape Sequences Constants

CS445 - Object Oriented Design and Programming

   

Data Types

For all data, assign a name (identifier) and a data type Data type tells compiler: – How much memory to allocate – Format in which to store data – Types of operations you will perform on data Compiler monitors use of data – Java is a "strongly typed" language Java "primitive data types"

byte, short, int, long, float, double, char, boolean CS445 - Object Oriented Design and Programming

Declaring Variables

   Every Variable must be given a name and a data type Variables hold one value at a time, but that value can change Syntax: or

dataType identifier;



dataType identifier1, identifier2, …;

Naming convention for variable names: – first letter is lowercase – embedded words begin with uppercase letter

CS445 - Object Oriented Design and Programming

Java Primitive Data Types



byte, short, int, long , float, double, char, boolean primitive integral boolean floating point byte char short int long float double CS445 - Object Oriented Design and Programming

OO Design

CS445 - Object Oriented Design and Programming

Topics

    Class Basics and Benefits Creating Objects Using Constructors Calling Methods Using Object References

CS445 - Object Oriented Design and Programming

Object-Oriented Programming

    Classes combine data and the methods (code) to manipulate the data Classes are a template used to create specific objects All Java programs consist of at least one class.

Two types of classes – Application/Applet classes – Service classes

CS445 - Object Oriented Design and Programming

Example



Student

class – Data: name, year, and grade point average – Methods: store/get the value of each piece of data, promote to next year, etc.



Student

Object: student1 – Data: Maria Gonzales, Sophomore, 3.5

CS445 - Object Oriented Design and Programming

Some Terminology

    

Object reference

: identifier of the object

Instantiating an object

: creating an object of a class

Instance of the class

: the object

Methods:

the code to manipulate the object data

Calling a method

: invoking a service for an object.

CS445 - Object Oriented Design and Programming

   

Class Data

Instance variables

: variables defined in the class and given values in the object

Fields

: instance variables and

static

(we'll define

static

later) variables

Members

methods of a class: the class's fields and Fields can be: – any primitive data type (

int

,

double

, etc.) – objects

CS445 - Object Oriented Design and Programming

Encapsulation

 Implementation of a module should be separated from its users.

 Instance variables are usually declared to be

private

, which means users of the class must reference the data of an object by calling methods of the class.

 Thus the methods provide a protective shell around the data. We call this

encapsulation

.

 Benefit: the class methods can ensure that the object data is always valid.

CS445 - Object Oriented Design and Programming

Modularity

  Divide-and-conquer Decompose a complex system into a highly cohesive loosely coupled modules.

– Cohesion single-mind-ness of a module • Each module should small and simple – Coupling the degree of connectivity between modules • Interactions between modules should be simple

CS445 - Object Oriented Design and Programming

Abstraction

  Separating the essential from the nonessential The behaviors of a module should be characterized in a precise way using its interfaces.

 Server provider for example is a client that provide services (methods) to it’s clients.

– Clients need to know only the contract API.

CS445 - Object Oriented Design and Programming

Polymorphism

   Many shapes Same method many ways to call it (dynamic) Replacing an object with its parent

CS445 - Object Oriented Design and Programming

Reusability



Reuse

: class code is already written and tested, so you build a new application faster and it is more reliable Example: A

Date

class could be used in a calendar program, appointment-scheduling program, online shopping program, etc.

CS445 - Object Oriented Design and Programming

How To Reuse A Class

 You don't need to know how the class is written.  You do need to know the

application programming interface

(

API

) of the class.

 The API is published and tells you: – How to create objects – What methods are available – How to call the methods

CS445 - Object Oriented Design and Programming

 

Declare an Object Reference

Syntax: ClassName objectReference; or ClassName objectRef1, objectRef2…; Object reference holds address of object Example: Date d1;

CS445 - Object Oriented Design and Programming

Instantiate an Object

    Objects MUST be instantiated before they can be used Call a constructor using

new

keyword Constructor has same name as class.

Syntax:  objectReference = new ClassName( arg list );

Arg list

(argument list) is comma-separated list of initial values to assign to object data

CS445 - Object Oriented Design and Programming

} 

Constructor

Constructor method special method with the same name as the class that is used with

new

when a class is instantiated

public class name

{

public name(String frst,String lst) { first = frst; last = lst; } Name name; name = new Name(“john”, “Dewey”);

CS445 - Object Oriented Design and Programming

Date

Class API

constructor

: special method that creates an object and assigns initial values to data

Date

Class Constructor Summary Date( ) creates a

Date

object with initial month, day, and year values of 1, 1, 2000 Date( int mm, int dd, int yy ) creates a

Date

object with initial month, day, and year values of

mm

,

dd

, and

yy

CS445 - Object Oriented Design and Programming

Instantiation Examples

Date independenceDay; independenceDay = new Date( 7, 4, 1776 ); Date graduationDate = new Date( 5, 15, 2008 ); Date defaultDate = new Date( );

} {

Constructors.java

public class Constructors } { public static void main( String [] args ) Date independenceDay; independenceDay = new Date( 7, 4, 1776 ); Date graduationDate = new Date( 5, 15, 2008 ); Date defaultDate = new Date( );

Objects After Instantiation

CS445 - Object Oriented Design and Programming

Calling a Method

CS445 - Object Oriented Design and Programming

Method Classifications



Accessor

methods – get… – gives values of object data 

Mutator

– set… methods – change values of object data

CS445 - Object Oriented Design and Programming

Return value

Date

Class Methods

Method name and argument list

int int int void void void getMonth( )

returns the value of month

getDay( )

returns the value of day

getYear( )

returns the value of year

setMonth( int mm )

sets the value of month to

mm

setDay( int dd )

sets the value of day to

dd

setYear( int yy )

sets the value of year to

yy

CS445 - Object Oriented Design and Programming

The Argument List in an API

 Pairs of dataType variableName   Specify – Order of arguments – Data type of each argument Arguments can be: – Any expression that evaluates to the specified data type

CS445 - Object Oriented Design and Programming

Modeling Relationships and Structures

 UML

CS445 - Object Oriented Design and Programming

UML Class Diagram

 Used to model the static structure and relationships among the classes of an OO software system  A class diagram is made of: – Nodes (Classes and Interfaces) – Links (Relationships)

CS445 - Object Oriented Design and Programming

Relationships

    Inheritance – Extension Relationship (specialization and generalization) – Extension between two interfaces – Implementation (when a class implements an interface) – UML uses hollow triangle pointing toward the super class – See Page 30 for an example Association Aggregation and Composition Dependency

CS445 - Object Oriented Design and Programming

Read Ahead

 Chapter 2 including the case study on page 44

CS445 - Object Oriented Design and Programming