CS1101X DG2

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CS1101X DG2

• Welcome!

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INTRODUCTION

• My name is Johannes Ardiant Harlie, 3rd year
  student majoring in Computer Engineering.
• You can call me Jo.
• e-mail johannes_at_nus.edu.sg
• SoC e-mail johannes_at_comp.nus.edu.sg
• Consultation virtually 24hrs ? as Ill check my
  e-mails regularly

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• Its time to introduce yourself ?

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DISCUSSION OUTLINE

• Short introduction
• Clarify some admin matters
• CourseMarker
• Lectures Revision (30 mins)
• Discussion of Questions
• Review of Trial Lab
• Any other business

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ADMINISTRATIVE MATTERS

• The discussion will be divided into 2 parts
• First one hour short review of previous lecture,
  discussion of tutorial questions, explanation
  solution of labs questions
• Next hour those who still have queries or
  unclear with some concepts, can stay back for
  consultation ?

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WHAT DO I EXPECT FROM YOU?

• Ill send you some questions to be prepared
  before coming to this discussion session. So
  please prepare to answer those questions since
  Ill ask some of you to present your answer to
  the class.
• ASK QUESTIONS if you dont understand! Thats
  what this discussion is for.

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What do you expect from me?
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COURSEMARKER

• Make sure that youve installed CM in your
  computer since the first lab will be out
  tomorrow.
• Further info from this site http//www.comp.nus.e
  du.sg/cmarker/
• Any difficulties in installation?

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OBJECT ORIENTED PROGRAMMING

• Whats object oriented programming?
• programming paradigm that uses "objects" and
  their interactions to design applications and
  computer programs (from Wikipedia)
• Visualization of object oriented programming
• Car and wheel paradigm

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• Whats the different between class and object?
• An object is a thing, both tangible and
  intangible. Account, Vehicle, Employee, etc.
• To create an object inside the computer program,
  we must provide a definition for objectshow they
  behave and what kinds of information they
  maintain called a class.
• An object is called an instance of a class.

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• Concept of message, method, and argument
• To instruct a class or an object to perform a
  task, we send a message to it.
• For a class or and object to process the message
  it receives, it must posses a matching method.
• Class method a method defined for a class
• Instance method a method defined for an object.
• A value we pass to an object is called an
  argument of a message.

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• Instance data values and class data values
• An instance data value is used to maintain
  information specific to individual instances. For
  example, each BankAccount object maintains its
  balance.
• A class data value is used to maintain
  information shared by all instances or aggregate
  information about the instances.

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• Inheritance, superclasses, and subclasses
• Inheritance is a mechanism in OOP to design two
  or more entities that are different but share
  many common features.
• Features common to all classes are defined in the
  superclass.
• The classes that inherit common features from the
  superclass are called subclasses.
• We also call the superclass an ancestor and the
  subclass a descendant.

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GETTING STARTED WITH JAVA

• Object declaration
• Object creation

Customer customer Student jan, jim,
jon Vehicle car1, car2
customer new Customer( ) jon new
Student(John Java) car1 new Vehicle( )
Examples
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• Program Components
• Comments
• Import statement
• Class declaration

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Comment
/ Chapter 2 Sample Program Displaying a
Window File Ch2Sample2.java / import
javax.swing. class Ch2Sample1 public
static void main(String args)
JFrame myWindow myWindow new JFrame(
) myWindow.setSize(300, 200) myWindow.setTit
le(My First Java Program) myWindow.setVisible
(true)
Import Statement
Class Declaration
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• Edit-compile-run cycle
• Type in the program using an editor and save the
  program into a file. This file is called a source
  file
• Compile the source file. The result is called
  bytecode file
• Execute the bytecode file. Java interpreter will
  go through bytecode file and execute instructions
  in it.

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NUMERICAL DATA

• Type of numerical data

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• Precedence Rule

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• Important concept
• Increment and Decrement

double r 8.32 double s s 2
r-- System.out.println("r "
r) System.out.println("s " s)
double r 8.32 double s s 2
--r System.out.println("r "
r) System.out.println("s " s)
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• Type Casting
• Explicit type casting
• using this syntax
• ( ltdata typegt ) ltexpressiongt
• example
• (float) x / 3
• (int) (x / y 3.0)
• Implicit type casting
• double x 3 5 //promotion is ok
• int x 3.5 //demotion is not allowed

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• Math class

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DISCUSSION OF SELECTED QUESTIONS

• Q.1
• Q.2.1, -.2, -.13, -.15
• Q.4
• Q.5.a, -.b
• Q.6
• Q.7

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REVIEW OF TRIAL LABS

• // CS1101 (AY2007/8 Semester 1)
• // Trial lab
• // Cube.java
• import java.util.
• public class Cube
• public static void main(String args)
• Scanner scanner new Scanner(System.in)
• System.out.print("Enter length ")
• int length scanner.nextInt()
• System.out.print("Enter width ")
• int width scanner.nextInt()
• System.out.print("Enter height ")
• int height scanner.nextInt()

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NEXT LAB?

• Comprises of 4 easy tasks
• Will be released on 28 August 2007, Tuesday,
  2359
• Advise start doing your lab as soon as possible!

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• End of Discussion 1