How To Design program

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What is Program?
• A computer program is a set of ordered instructions
for a computer to perform a specific task or to exhibit
desired behaviors.
• Without programs, computers are useless.

• A software application or software program is the

most commonly found software on the computer.
– Microsoft Word is a word processor program that
allows users to create and write documents.

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What is Programming?
• Computer programming is the process of
designing, writing, testing, debugging, and
maintaining the source code of computer programs.
• Programming language:
– The source code of program is written as a series of
human understandable computer instructions in a that
can be read by a compiler, and translated into
machine code so that a computer can understand and
run it.
– There are many programming languages such as
C++, C#, Java, Python, Smalltalk, etc.

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Design Program
• The process of programming often requires
expertise in many different subjects,
including knowledge of the application domain,
specialized algorithms and formal logic.
• Main goal of the design process is to lead from
problem statements to well-organized solutions
• Design guidelines are formulated as a number of
program design recipes.
– A design recipe guides a beginning programmer
through the entire problem-solving process

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How to Design Program
To design a program properly, a programmer must:
1. Analyze a problem statement,
typically stated as a word problem;
2. Express its essence, abstractly and with
examples;
3. Formulate statements and comments in a precise
language;
4. Evaluate and revise these activities in light of
checks and tests; and
5. Pay attention to details.
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Why Java?
• Object-oriented programming languages
• Open source
• A cross platform language
– Portability: "Write Once, Run Anywhere"
• Spread Rapidly through WWW and Internet

• JVM (Java Virtual Machine)

• JRE (Java Runtime Environment)
• JDK (Java Developer Kit)

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IDE
• IDE: Integrated Development Environment
– Netbean: supported by Sun
– Eclipse: open source, supported by IBM

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The Varieties of Data

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Topic
• Primitive Forms of Data
• Compound Data: Class
– Design Class
• Class References, Object Containment
• Design method

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Primitive Forms of Data
• Java provides a number of built-in atomic forms of
data with which we represent primitive forms of
information.

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Integer type
Name Size Range
byte 1 byte -128 … 127
short 2 bytes -32,768 … 32,767
int 4 bytes -2,147,483,648 to
2,147,483,648
long 8 bytes -9,223,372,036,854,775,808 to
9,223,372,036,854,775,808

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Decimal type

Name Size Range

float 4 bytes ±1.4 x 10-45 to ±3.4 x 1038

double 8 bytes ±4.9 x 10-324 to ±1.8 x 10308

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Character type
Java represent a Unicode character (2 bytes)

Name Size Range

char 2 bytes \u0000 … \uFFFF

• Q: Distinguish char type and String type ?

• A:
– char c = 't';
– String s = "tin hoc";
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Boolean type

Name Size Range

boolean 1 byte false, true

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String
• Strings to represent symbolic.
Symbolic information means the names of people,
street addresses, pieces of conversations, …
• a String is a sequence of keyboard characters
enclosed in quotation marks
– "bob"
– "#$%ˆ&"
– "Hello World"
– "How are U?"
– "It is 2 good to B true."

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 Compound Data: Class

• For many programming problems, we need more

than atomic forms of data to represent the relevant
information.

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Coffee Example
Consider the following problem:
• Develop a program that keeps track of coffee sales
at a specialty coffee seller. The sales receipt must
include the kind of coffee, its price (per pound), and
its weight (in pounds).

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Coffee sale infomation
• The program may have to deal with hundreds and
thousands of sales.
• We need to keep all pieces of information about a
coffee sale together in one place.
• The information for a coffee sale consists of three
(relevant) pieces: the kind of coffee, its price, and
its weight. For example, the seller may have sold:
1) 100 pounds of Hawaiian Kona at $15.95/pound
2) 1,000 pounds of Ethiopian coffee at $8.00/pound
3) 1,700 pounds of Colombian Supreme at $9.50/pound

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Define Java Class, Constructor
• We would have used a class of structures to
represent such coffee sales: class
– a coffee class has three fields: kind, price, and weight.
– the constructor is to get the values of the three fields
class Coffee { class definition
String kind;
double price; Field declarations. Each declaration specifies
double weight; the type of values that the field name represents.

Coffee(String kind, double price, double weight) {

this.kind = kind;
this.price = price;
this.weight = weight;
CONSTRUCTOR
}
of the class
}
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About Constructor
• Constructor name is same class name.
• The parameters of a constructor enclose in ()
quotes, separated by commas (,).
• Its body is a semicolon-separated (;) series of
statement this.fieldname = parametername;

Coffee(String kind, double price, double weight) {

this.kind = kind;
this.price = price;
this.weight = weight;
}

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Class Diagram: abstractly express
Class Name

Coffee
- String kind
Property
Data type - double price or field
- double weight
Method

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Translate sample
• It is best to translate some sample pieces of
information into the chosen representation.
• This tests whether the defined class is adequate for
representing some typical problem information.
• Apply the constructor to create an object (instance)
of the Coffee class:
– new Coffee("Hawaiian Kona", 15.95, 100)
– new Coffee("Ethiopian", 8.00, 1000)
– new Coffee("Colombia Supreme", 9.50, 1700)

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Test Class
Import test unit library
Define class CoffeeTest is test
import junit.framework.*; case.

public class CoffeeTest extends TestCase {

Test method that name is testXXX
public void testConstructor() {
new Coffee("Hawaiian Kona", 15.95, 100);
new Coffee("Ethiopian", 8.0, 1000);
new Coffee("Colombian Supreme ", 9.5, 1700);
}
}

This tests contain statement to create an object of the Coffee class,

you apply the constructor to as many values as there are parameters:
new Coffee("Hawaiian Kona", 15.95, 100)
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Date example
• Develop a program that helps you keep track of
daily. One date is described with three pieces of
information: a day, a month, and a year

• Class diagram

Date
- int day
- int month
- int year

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Define Class, Constructor and Test
class Date {
int day;
int month;
int year;
Date(int day, int month, int year) {
this.day = day;
this.month = month;
this.year = year;
}
}

import junit.framework.*;
public class DateTest extends TestCase {
public void testConstrutor() {
new Date(5, 6, 2003); // denotes June 5, 2003
new Date(6, 6, 2003); // denotes June 6, 2003
new Date(23, 6, 2000); // denotes June 23, 2000
}
}
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GPS Location example
• Develop a GPS navigation program for cars. The
physical GPS unit feeds the program with the
current location. Each such location consists of two
pieces of information: the latitude and the longitude.

• Class diagram
GPSLocation
- double latitude
- double longitude

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Define Class, Constructor and test
class GPSLocation {
double latitude; /* degrees */
double longitude; /* degrees */
GPSLocation(double latitude, double longitude) {
this.latitude = latitude;
this.longitude = longitude;
}
}

import junit.framework.*;
public class GPSLocationTest extends TestCase {
public void testConstructor() {
new GPSLocation(33.5, 86.8);
new GPSLocation(40.2, 72.4);
new GPSLocation(49.0, 110.3);
}
}
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Three steps in designing Classes
1. Read the problem statement.
Look for statements that mention or list the
attributes of the objects in your problem space.
Write down your findings as a class diagram
because they provide a quick overview of classes.
2. Translate the class diagram into a class definition,
adding a purpose statement to each class.
3. Obtain examples of information and represent
them with instances of the class.
Conversely, make up instances of the class and
interpret them as information.
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 Class References,
Object Containment

• Sometimes information not only consist of several

pieces of information, but one of its constituents
consists of several pieces, too.

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Runner's training log
Take a look at this problem:
• Develop a program that manages a runner's training
log. Every day the runner enters one entry
concerning the day's run. Each entry includes the
day's date, the distance of the day's run, the
duration of the run, and a comment describing the
runner's post-run feeling.

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Log Entry examples
• A log entry consists of four pieces of information: a
date, a distance, a duration, and a comment.
– To represent the last three, we can use primitive
types; double (in miles), int (in minutes), and String
– Representation for dates consists of three pieces:
day, month, year
• Examples:
– on June 5, 2003: 5.3 miles in 27 minutes, feeling
good;
– on June 6, 2003: 2.8 miles in 24 minutes, feeling tired
– on June 23, 2003: 26.2 miles in 150 minutes, feeling
exhausted; 31
Class Diagram
Class Reference

Entry
Date
- Date date
- int day
- double distance
- int month
- int duration
- int year
- String comment

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 Define class and constructor
class Entry {
Date date; class reference
double distance;
int duration;
String comment;
Entry(Date date, double distance, int duration,
String comment) {
this.date = date; class Date {
this.distance = distance; int day;
this.duration = duration; int month;
this.comment = comment; int year;
} Date(int day, int month,
} int year) {
this.day = day;
this.month = month;
this.year = year;
}
}
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Test constructor
object containment
import junit.framework.*;
public class EntryTest extends TestCase {

public void testConstructor() {

new Entry(new Date(5, 6, 2004), 5.3, 27, "good");

new Entry(new Date(6, 6, 2004), 2.8, 24, "tired");

Date date1 = new Date(23, 6, 2004);

new Entry(date1, 26.2, 159, "exhausted");
}
}

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Restaurant example
• Develop a program that helps a visitor navigate
Manhattan's restaurant scene. The program must be
able to provide four pieces of information for each
restaurant: its name, the kind of food it serves,
its price range, and the closest intersection
(street and avenue). avenue
• Examples:
– La Crepe, a French restaurant, on 7th Ave and 65th Street,
moderate;
– Bremen Haus, a German restaurant on 2nd Ave and 86th Street,
moderate;
– Moon Palace, a Chinese restaurant on 10th Ave and 113th
Street, inexpensive;
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Class Diagram

Restaurant
- String name Intersection
- String food - int avenue
- String priceRange - int street
- Intersection intersection

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Define class and constructor
class Restaurant {
String name;
String food;
String priceRange; reference
Intersection intersection;
Restaurant(String name, String food,
String priceRange, Intersection intersection) {
this.name = name;
this.food = food;
this.priceRange = priceRange;
this.intersection = intersection;
}
} class Intersection {
int avenue;
int street;
Intersection(int avenue, int street) {
this.avenue = avenue;
this.street = street;
} 37
Test constructor
import junit.framework.*;
public class RestaurantTest extends TestCase {

public void testConstructor() {

new Restaurant("La Crepe", "French", "moderate",
new Intersection(7, 65));
new Restaurant("Bremen Haus", "German", "moderate",
new Intersection(2, 86));
Intersection intersection1 = new Intersection(10, 113);
new Restaurant("Moon Palace", "Chinese", " inexpensive",
intersection1);
}
}

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Rectangle example
• The rectangles have width, height and are located
on the Cartesian plane of a computer canvas, which
has its origin in the northwest corner.

Rectangle
CartPt
- CartPt location
- int x
- int width
- int y
- int height

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Define class and constructor
class CartPt {
int x;
int y;
CartPt(int x, int y) {
this.x = x;
this.y = y;
}
} class Rectangle {
CartPt location;
int width;
int height;
Rectangle(CartPt location, int width, int height) {
this.location = location;
this.width = width;
this.height = height;
}
}
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Test constructor
import junit.framework.*;

public class RectangeTest extends TestCase {

public void testContructor() {

CartPt p = new CartPt(3, 4);
CartPt q = new CartPt(5, 12);

new Rectangle(p, 5, 17);

new Rectangle(q, 10, 10);
new Rectangle(new CartPt(4, 3), 5, 12);
}
}

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