ECE 242 Spring 2003 Data Structures in Java

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ECE 242 Spring 2003Data Structures in Java

• http//rio.ecs.umass.edu/ece242
• Object-Oriented Programming (1)
• Prof. Lixin Gao

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Todays Topics

• Object Oriented Design
• Class
• Instance variables
• Methods
• Constructor

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Cartoon
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Object Oriented Design

• Describe real world as well as virtual world
• How?
• Procedural-Oriented Programming
• A sequence of actions
• Object-Oriented Programming
• Describe objects

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Object Oriented Design
World
Class
Class
Class attributes behavior
Object
Object
Object
Class

• Class a generic description for a set of objects.

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Car

• Attribute
• id
• model
• year build
• color
• Behavior
• start the engine
• stop the engine
• speed up
• change gear

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Employee

• Attribute
• name
• telephone
• Behavior
• print information
• change telephone

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MP3 file

• Attribute
• title
• artist
• Behavior
• start playing song
• stop playing song

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Movie

• Attribute
• title
• cinema
• rating
• star
• votes for Oscar
• Behavior
• nominate for Oscar

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Bank

• Attribute
• bank name
• bank address
• checking interest
• saving interest
• Behavior
• change address
• change checking interest
• change saving interest
• print information

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Object

• Attribute
• Behavior

• Instance variable
• Method/Function

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Class Definition

• class
• instance variables
• methods
• constructor

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Organization of Class

• class OurClass
• int firstMethod()
• int secondMethod(float f)
• OurClass() // constructor
• //end of class OurClass

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Employee

• Create a class for Employee
• Attribute
• name
• telephone number
• Behavior
• print information (name telephone)

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Employee Class

• class Employee
• String name
• String tel
• public void printinfo()
• System.out.println(name"'s number is
  "tel)

Attribute name telephone
Behavior printinfo()
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MP3 Song

• Create a class for MP3 Song
• Attribute
• title
• artist
• Behavior
• start playing song
• stop playing song

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MP3 Class

• class MP3
• String title
• String artist
• public void startPlaying()
• // Call Windows MediaPlayer to start
  playing song
• public void stopPlaying()
• // Call Windows MediaPlayer to stop playing
  song

Attribute title, artist
Behavior start/stop song
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Bank

• Create a class for Bank
• Attribute
• name
• address
• checking Interest
• saving Interest
• Behavior
• change address
• change checking interest
• change saving interest
• print information

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Bank Class --- Attribute

• class Bank
• String name
• String address
• double checkingInterest
• double savingInterest

Attribute name, address, checking interest and
saving interest
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Bank Class --- Behavior

• void changeAddress(String newaddress)
• address newaddress
• void changeCheckingInterest(double val)
• checkingInterest val
• void changeSavingInterest(double val)
• savingInterest val

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Bank Class --- Behavior

• void printinfo()
• System.out.println(bank name is name )
• System.out.println(bank address is
  address)
• System.out.println(checking interest is
  checkingInterest)
• System.out.println(saving interest is
  savingInterest)

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Constructor

• Special method
• Name is the same as class
• Initialize instance variable

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Employee Class with Constructor

• class Employee
• String name
• String tel
• public void printinfo()
• System.out.println(name"'s number is
  "tel)
• Employee( String n, String t )
• name n
• tel t

Constructor
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Create Object

• new Create a new object of a class
• Employee gaonew Employee("Gao", "4548")
• gao.printinfo()
• Method and instance variables
• gao is an object
• printinfo() is a method belong to object gao

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Executable

• Make java file executable
• main method
• Syntax
• public static void main(String args)

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Executable Employee Class

• Make class executable (Employee.java)
• public static void main(String args)
• //where program gets executed
• Employee gaonew Employee("Gao", "4548")
• gao.printinfo()

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MP3 Class with Constructor

• class MP3
• String title
• String artist
• MP3( String t, String a)
• title t
• artist a

Constructor
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Create MP3 Object

• create MP3 object
• MP3 bye new MP3("Bye Bye Bye", "NSync")
• MP3 brand new MP3(Brand New Day", Sting")
• Behaviors for these objects
• bye.startPlaying()
• bye.stopPlaying()
• brand.startPlaying()