cs1101x: programming methodology recitation 4 design issues and problem solving

CS1101X: Programming Methodology

Recitation 4 Design Issues and

Problem Solving

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Problem Statement

Write an application that computes the total charges for the overdue library books.

For each library book, the user enters the due date and (optionally) the overdue charge per day,the maximum charge, and the title.

If the optional values are not entered, then the preset default values are used.

A complete list of book information is displayed when the user finishes entering the input data.The user can enter different return dates to compare the overdue charges.

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Overall Plan

Tasks:1. Get the information for all books

2. Display the entered book information

3. Ask for the return date and display the total charge. Repeat this step until the user quits.

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Required Classes

OverdueChecker Scanner

LibraryBook

helper class

BookTracker

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Development Steps

We will develop this program in five steps:

1. Define the basic LibraryBook class.

2. Explore the given BookTracker class and integrate it with the LibraryBook class.

3. Define the top-level OverdueChecker class. Implement the complete input routines.

4. Complete the LibraryBook class by fully implementing the overdue charge computation.

5. Finalize the program by tying up loose ends.

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Step 1: Design

Develop the basic LibraryBook class. The key design task is to identify the data

members for storing relevant information. We will include multiple constructors for ease

of creating LibraryBook objects. Make sure that an instance will be initiated correctly

no matter which constructor is used.

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Step 1: Code

Directory: Chapter7/Step1

Source Files: LibraryBook.java Step1Main.java (test program)

Directory: Chapter7/Step1

Source Files: LibraryBook.java Step1Main.java (test program)

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Step 1: Code LibraryBook (1/5)import java.util.*;import java.text.*;

class LibraryBook {

// default values private static final double CHARGE_PER_DAY = 0.50; private static final double MAX_CHARGE = 50.00; private static final String DEFAULT_TITLE = "Title unknown"; private GregorianCalendar dueDate; private String title; private double chargePerDay; private double maximumCharge;

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Step 1: Code LibraryBook (2/5)

// Constructors: public LibraryBook(GregorianCalendar dueDate) { this(dueDate, CHARGE_PER_DAY); } public LibraryBook(GregorianCalendar dueDate, double chargePerDay) { this(dueDate, chargePerDay, MAX_CHARGE); }

public LibraryBook(GregorianCalendar dueDate, double chargePerDay, double maximumCharge) { this(dueDate, chargePerDay, maximumCharge, DEFAULT_TITLE); }

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Step 1: Code LibraryBook (3/5)

public LibraryBook(GregorianCalendar dueDate, double chargePerDay, double maximumCharge, String title) { setDueDate(dueDate); setChargePerDay(chargePerDay); setMaximumCharge(maximumCharge); setTitle(title); }

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Step 1: Code LibraryBook (4/5)

//-------------------------------------------------// Public Methods:// double getChargePerDay( )// GregorianCalendar getDueDate( )// double getMaxCharge( )// String getTitle( )//// void setChargePerDay(double)// void setDueDate(GregorianCalendar )// void setMaxCharge(double)// void setTitle(String)//// String toString( )//------------------------------------------------

// actual codes omitted

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Step 1: Code LibraryBook (5/5) // Returns the string representation of this book in the // format <title> <charge per day> <max chanrge> <due date> public String toString( ) {

String tab = "\t"; SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yy"); DecimalFormat df = new DecimalFormat("0.00"); return getTitle() + tab + "$ " + df.format(getChargePerDay()) + tab + "$ " + df.format(getMaxCharge()) + tab + sdf.format(dueDate.getTime()); }}

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Step 1: Code Step1Main (1/2)

import java.util.*;class Step1Main { public static void main( String[] args ) { //Create 4 LibraryBook objects and output them GregorianCalendar dueDate, returnDate; LibraryBook book1, book2, book3, book4; returnDate = new GregorianCalendar(2004, Calendar.MARCH, 15); dueDate = new GregorianCalendar(2004, Calendar.MARCH, 14); book1 = new LibraryBook(dueDate); dueDate = new GregorianCalendar(2004, Calendar.FEBRUARY, 13); book2 = new LibraryBook(dueDate, 0.75); book2.setTitle("Introduction to OOP with Java");

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Step 1: Code Step1Main (2/2)

dueDate = new GregorianCalendar(2004, Calendar.JANUARY, 12); book3 = new LibraryBook(dueDate, 1.00, 100.00); book3.setTitle("Java for Smarties");

dueDate = new GregorianCalendar(2004, Calendar.JANUARY, 1); book4 = new LibraryBook(dueDate, 1.50, 230.00, "Me and My Java"); System.out.println(book1); System.out.println(book2); System.out.println(book3); System.out.println(book4); }}

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Notes

Note how the LibraryBook class is designed. What are its data members? How are the constructors written? How are the accessors and mutators written?

Read up the subsequent steps yourself.

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MyTriangle.java (1/7)// CS1101 (AY2005/6 Semester 1)// Lab 3 Task 1// MyTriangle.java// Aaron Tan/** * This class contains selected properties of a triangle: * lengths of its sides, type (equilateral, isosceles * or scalene), and whether it is a right triangle. */import java.util.*;

class MyTriangle { // Codes for triangle types public static final int IS_EQUILATERAL = 0; public static final int IS_ISOSCELES = 1; public static final int IS_SCALENE = 2;

// For checking for right triangle public static final double EPSILON = 0.001;

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MyTriangle.java (2/7)

// Data members private double sideX, sideY, sideZ; // the 3 sides private int triangleType; // type: 0 = equilateral; // 1 = isosceles; 2 = scalene private boolean isRight; // Right triangle?

// Constructor public MyTriangle(double x, double y, double z) { sideX = x; sideY = y; sideZ = z; }

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MyTriangle.java (3/7)

/-------------------------------------------------// Public Methods:// void setSideX ( double );// void setSideY ( double );// void setSideZ ( double );// void setType ( int );// void setIsRight ( boolean );// double getSideX ( );// double getSideY ( );// double getSideZ ( );// int getType ( );// boolean getIsRight ( );//------------------------------------------------

// codes omitted

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MyTriangle.java (4/7)

// main method used to test the MyTriangle class public static void main (String [] args) {

Scanner scanner = new Scanner(System.in);

System.out.print("Enter 3 sides: "); double side1 = scanner.nextDouble(); double side2 = scanner.nextDouble(); double side3 = scanner.nextDouble();

// To read until a valid set of sides are entered while (side1 + side2 <= side3) { System.out.print("Enter 3 sides again: "); side1 = scanner.nextDouble(); side2 = scanner.nextDouble(); side3 = scanner.nextDouble(); }

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MyTriangle.java (5/7)

MyTriangle tri = new MyTriangle(side1, side2, side3);

System.out.println("Sides are " + tri.getSideX() + " " + tri.getSideY() + " " + tri.getSideZ());

// Determine triangle type if (side1 == side2 && side2 == side3) { tri.setType(IS_EQUILATERAL); } else if (side1 == side2 || side1 == side3 || side2 == side3 ) { tri.setType(IS_ISOSCELES); } else { tri.setType(IS_SCALENE); }

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MyTriangle.java (6/7)

// Determine if triangle is right-angled // using Pythagoras' Theorem. double tempValue = Math.abs((side1 * side1 + side2 * side2) - (side3 * side3)); tri.setIsRight(tempValue <= EPSILON);

// Output System.out.print("Type is "); switch (tri.getType()) { case IS_EQUILATERAL: System.out.println("equilateral."); break; case IS_ISOSCELES: System.out.println("isosceles."); break; case IS_SCALENE: System.out.println("scalene."); }

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MyTriangle.java (7/7)

System.out.print("Triangle "); if (tri.getIsRight()) System.out.println("is right."); else System.out.println("is not right."); }}

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Task: Factorisation (1/4)

Past PE question Time limit: 30 minutes Write a program to read in a non-zero integer

and display the factorisation. Examples:

Enter n: 8 8 = 1 * 2 * 2 * 2

Enter n: -300

-300 = -1 * 2 * 2 * 3 * 5 * 5

Enter n: 77

77 = 1 * 7 * 11

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Task: Factorisation (2/4)

Scanner scanner = new Scanner(System.in);System.out.print("Enter n: ");int n = scanner.nextInt();

if (n > 0) System.out.print(n + " = 1");else System.out.print(n + " = -1");

int factor = 2;while (n > 1) { if (n % factor == 0) { System.out.print(" * " + factor); } else factor++;}System.out.println(); Note: This code does not

work for negative value of n. Correct it.

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Task: Factorisation (3/4)

Scanner scanner = new Scanner(System.in);System.out.print("Enter n: ");int n = scanner.nextInt();start(n);

Modular programming.

private static void start(int value) { if (value > 0) System.out.print(value + " = 1"); else System.out.print(value + " = -1");

int factor = 2; while (value > 1) { if (value % factor == 0) { System.out.print(" * " + factor); } else factor++; } System.out.println();}

But this method is not cohesive. (Why?)

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Task: Factorisation (4/4)Scanner scanner = new Scanner(System.in);System.out.print("Enter n: ");int n = scanner.nextInt();String answer = start(n); System.out.println(answer);

private static String start(int value) { String ans = ""; if (value > 0) ans += value + " = 1"; else ans += value + " = -1";

int factor = 2; while (value > 1) { if (value % factor == 0) { ans += " * " + factor; } else factor++; } return ans;}

Now this is cohesive.

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End of Recitation #4