CS1101: Programming Methodology http://www.comp.nus.edu.sg/~cs1101x/

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CS1101 Programming Methodology
http//www.comp.nus.edu.sg/cs1101x/
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Java Appreciation
Java Appreciation

• OR
• Whats In Store In CS1101?

by Aaron Tan 28 July 2008, 9am, LT16
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Exercising Your Choice

• CS1101
• or
• CS1101S

Java
Scheme
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CS1101 Course Description

• This module introduces the fundamental concepts
  of programming from an object-oriented
  perspective, and is perceived as the first and
  foremost introductory course to computing.

No prior experience is assumed.
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CS1101 Objectives

• Learning about programming methodology and
  principles, using the object-oriented model.
• Outcomes
• Know how to solve simple algorithmic problems.
• Know how to write good small programs.
• JAVA is merely a tool.
• This is not a course on just JAVA alone!

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CS1101 Lecture Groups

• Group X (3 lecture groups)
• Mr Aaron Tan Tuck Choy (Module coordinator)
• For students with more experience
• Group Y (3 lecture groups)
• A/P Wynne Hsu
• Dr Razvan Voicu
• A/P Lee Mong Li
• Group Z (3 lecture groups)
• A/P Tan Chew Lim
• Dr Anthony Fang
• Mr Henry Chia

CS1101X, Y and Z all cover the same syllabus, and
have common tests. Final grading of CS1101X, Y
and Z is done together as a single group.
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Module Website

• http//www.comp.nus.edu.sg/cs1101x/

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Workload (5 MCs)

• Lectures
• 3 hours/week in a lab setting.
• Discussion
• 2 hours/week in a lab setting.
• Continual assessment
• Lab assignments
• Mid-term test
• Practical Exam

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Skills Set (1/2)

• Java constructs

Problem solving
Program
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Skills Set (2/2)

• Java constructs (transferable skills)
• Class and objects types and variables control
  constructs (selection, repetition) APIs arrays
  exceptions applications (searching, sorting).
• Problem solving (more transferable skills)
• Programming methodology (development cycle,
  top-down design, modularity) testing and
  debugging abstraction.
• Others
• Software tools (editor, compiler, debugger,
  CourseMarker) mathematical maturity.

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A Java Program (Hello.java)
Comments

• // Display a message.
• public class Hello
• public static void main(String args)
• System.out.println("Hello World!! -D")

Class name
Method name
Output
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A Java Program (Welcome.java)
API package

• // Author Aaron Tan
• // Purpose Ask for users name and display a
  welcome message.
• import java.util.
• public class Welcome
• public static void main(String args)
• Scanner scanner new Scanner(System.in)
• System.out.print("What is your name? ")
• String name scanner.next()
• System.out.println("Hi " name ".")
• System.out.println("Welcome to CS1101!\n")

Creating a Scanner object
Input
An object of class String
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Object-Oriented Programming (OOP)

• The fundamental OOP concept
• An object-oriented program uses objects.
• Demo on BlueJ
• Illustrate concepts of object and class
• Creation of objects
• Sending messages to objects

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Objects and classes (1/2)

• Object-oriented language
• Models real-world objects you find in everyday
  life.
• Objects
• Represent things from the real world, or from
  some problem domain (that red 1200cc Honda car,
  my 2-year old Persian cat with a short tail).
• Have name, state (set of values for its
  attributes) and behaviors (via methods).
• Perform actions or interact by sending messages.
• Classes
• Represent all objects of a kind (car, cat).
• A class is a model/blueprint/prototype for an
  object. An object is an instance of a class.
  Many instances (objects) can be created from a
  single class.

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Objects and classes (2/2)

• Class is a concept object is a concrete entity.
• A class defines what attributes an object has,
  but each object stores it own set of values,
  which contribute its state.
• Example PlayingCards is a class, whose
  properties are rank and suit. The queen of clubs
  and nine of diamonds are two instances (objects)
  of this class.
• New class (type of objects) can be derived from
  an existing class.
• Superclass and subclass the subclass
  extends/specializes the functionality of the
  superclass and inherits the properties and
  behaviors of the superclass.

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BlueJ

• Designed at Monash University, Australia.
• Runs on top of Sun Microsystems Java Development
  Kit (JDK).
• Provides an Integrated Development Environment
  (IDE) with editor, compiler and debugger.
• Simple user interface, easy to use. Do not need
  to write complete application.
• Refer to course website http//www.comp.nus.edu.sg
  /cs1101x/ (click on Resources ? Online)
• Download BlueJ and its documentation.

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BlueJ Creating objects (1/4)

• Choose example shapes.
• Classes Square, Circle, Triangle, Canvas.

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BlueJ Creating objects (2/4)

• Creating a new object

Right click on Circle class and choose new
Circle() to create a new Circle object. Circle()
is a constructor.
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BlueJ Creating objects (3/4)

• Creating a new object

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BlueJ Creating objects (4/4)

• Creating a new object

A new Circle object circle1 is created.
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BlueJ Calling methods (1/3)

• Methods implement the behavior of the objects.

Right click on the circle1 object and select the
makeVisible() method.
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BlueJ Calling methods (2/3)

• Methods implement the behavior of the objects.

Experiment with other methods makeInvisible(),
moveDown(), moveRight().
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BlueJ Calling methods (3/3)

• Methods with parameters
• changeColor(newcolor), changeSize(newDiameter),
  moveHorizontal(distance).

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BlueJ State (1/2)

• State the set of values of all the attributes of
  an object.

Right click on the circle1 object and select the
Inspect function.
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BlueJ State (2/2)

• Objects of the same class have the same
  fields/attributes. But each object may have it
  own set of values for its attributes.

State of circle1 object. Fields int
diameter int xPosition int yPosition String
Color boolean isVisible
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BlueJ Source code (1/8)

• Right click on class Circle and select Open
  Editor.

import java.awt. import java.awt.geom. /
A circle that can be manipulated and that draws
itself on a canvas. _at_author Michael
Kolling and David J. Barnes _at_version 1.0 (15
July 2000) / public class Circle private
int diameter private int xPosition private
int yPosition private String color private
boolean isVisible
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BlueJ Source code (2/8)
// Create a new circle at default position
with default color. public Circle( )
diameter 30 xPosition 20
yPosition 60 color "blue"
isVisible false // Make this circle
visible. If it was already visible, do nothing.
public void makeVisible( ) isVisible
true draw( ) // Make this
circle invisible. If it was already invisible, do
nothing. public void makeInvisible( )
erase( ) isVisible false
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BlueJ Source code (3/8)
// Move the circle a few pixels to the right.
public void moveRight( )
moveHorizontal(20) // Move the circle a
few pixels to the left. public void moveLeft(
) moveHorizontal(-20) //
Move the circle a few pixels up. public void
moveUp( ) moveVertical(-20)
// Move the circle a few pixels down. public
void moveDown( ) moveVertical(20)
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BlueJ Source code (4/8)
// Move the circle horizontally by 'distance'
pixels. public void moveHorizontal(int
distance) erase( ) xPosition
distance draw( ) // Move the
circle vertically by 'distance' pixels. public
void moveVertical(int distance) erase(
) yPosition distance draw( )

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BlueJ Source code (5/8)
// Slowly move the circle horizontally by
'distance' pixels. public void
slowMoveHorizontal(int distance) int
delta if (distance lt 0)
delta -1 distance -distance
else delta 1
for (int i 0 i lt distance i)
xPosition delta draw( )

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BlueJ Source code (6/8)
// Slowly move the circle vertically by
'distance' pixels. public void
slowMoveVertical(int distance) int
delta if (distance lt 0)
delta -1 distance -distance
else delta 1
for (int i 0 i lt distance i)
yPosition delta draw( )

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BlueJ Source code (7/8)
// Change the size to the new size (in
pixels). // Size must be gt 0. public void
changeSize(int newDiameter) erase( )
diameter newDiameter draw( )
// Change the color. Valid colors are
"red", "yellow", // "blue", "green",
"magenta" and "black". public void
changeColor(String newColor) color
newColor draw( )
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BlueJ Source code (8/8)
// Draw the circle with current specifications
on screen. private void draw( ) if
(isVisible) Canvas canvas
Canvas.getCanvas( ) canvas.draw(this,
color, new
Ellipse2D.Double(xPosition, yPosition,
diameter,
diameter)) canvas.wait(10)
// Erase the circle on screen. private
void erase( ) if (isVisible)
Canvas canvas Canvas.getCanvas( )
canvas.erase(this)
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Problem Solving (1/3)

• Problem ? Algorithm ?Program
• Task 1 Anagram
• Text that is formed by rearrangement of letters.
• Examples
• Dear
• Astronomer
• The Eyes
• The Morse Code
• A Decimal Point

Read Moon Starer They See Here Come Dots Im A
Dot In Place
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Problem Solving (2/3)

• Task 2 Maze

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Problem Solving (3/3)

• Task 3 Sudoku

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Think About It

• This set of slides will be available at
• http//www.comp.nus.edu.sg/cs1101x
• Administrative and registration issues
• Please attend Course Briefing later important!
• LT17, 28 July _at_ 2pm
• (after Deans Welcome Tea)
• Questions?

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