Mutable immutable (lập TRÌNH cơ bản SLIDE)

Define Class Define classpublic class Star { private String firstName; private String lastName; private String instrument; private int sales; private String lastName; private String

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Date example

Class

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public class TestDate extends TestCase {

public void testConstrutor(){

new Date(5, 6, 2003); // denotes June 5, 2003

}

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GPS Location example

program with the current location Each such location consists of two pieces of information: the latitude and the longitude

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Define Class, Constructor and test Constructor

class GPSLocation {

double latitude /* degrees */;

double longitude /* degrees */;

GPSLocation(double latitude, double longitude) {

public class TestGPSLocation extends TestCase {

public void testConstrutor(){

new GPSLocation (33.5, 86.8);

}

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A class is a generic description of a “thing” It has:

Attributes = Properties = Information = Fields = Data = Variables

Behaviors = Methods = Functions = Operations

3 State: describes the state that “thing” belongs to

A “thing” in a computer system ‘come alive – they have behavior

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Car example

With a Car

– when a car in good shape, it is in use state,

– When it is damaged, it becomes not workable state,

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Book example

A Book in library has:

• Attributes that we concern : name, author, publisher, price,…

• Behaviors can modeled with this book: borrow, payback,…

• States:

– If it is ready to be borrow, it in ready state

– if it is borrowed, it becomes busy state

– when it is old, damaged and taken stock of, it is in out of stock (thanh lý) state.

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Room example

A Room in hotel has:

• Attributes we concern: name, kind (may be: usual, deluxe, VIP,…), price per day,…

• Behavior can happen with a room: rent,…

– If it is ready to be rent, it is in ready state

– if it is rent, it becomes busy state

– when it is damaged, it is in-correct (sửa chữa) state

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Point example

A point in monitor has:

• Attributes: x coordinate , which tells us where the pixel is in the horizontal direction, and y

coordinate , which tells us where the pixel is located in the downwards vertical direction and color

• Behaivors:

– Computes how far some pixel is from the origin

– Computes the distance between 2 pixels,…

• State: ?

So, some real-life objects do not have state.

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– Compute his average score.

– Check whether the student is supervised by some teacher,

– Transfer this student for another head teacher.

• State: ?

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Object

• An object is an instance of a class

• Example:

– The Land Cruiser, red color and speed is 300 km/h is an instance of Car class.

– The For Escape, white color and speed is 250 km/h is an instance of Car class.

– The book Harry Porter, author is Rowling J.K, is published by Amazon, price 20$ is an instance of Book class.

– The book Nhat ky Dang Thuy Tram, author is Dang Thuy Tram, published by Tuoi Tre, price 3$ is an instance of Book class – The deluxe room- No 201, price 50 $ per day is an instance of Room class.

– A red point (2,3) is an instance of Point class.

– The student Nguyen Van A, his head teacher is Miss Thuy, has 8 in Math, 9 in Physic and 7 in Chemistry is is an instance of

Student class.

– A rectangle has height 5 cm, width 3 cm, north west point (2,3) is an instance of Rectangle class.

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• None modifier: Classes in the same package can access this attribute / method.

• public : Classes in all packages can access this attribute / method.

• private : Only the class itself can access this attribute / method.

The public or private modifiers for attribute and method

Encapsulation

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Group discussion

• Find more class examples in real life?

• Find more class examples in real life which do not have behavior, then add

their behavior?

•Distinguish class and instance of class (object).

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Star example

name , instrument he uses and his sales

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Property or field

MethodData type

Class

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Define Class

Define classpublic class Star { private String firstName;

private String lastName;

private String instrument;

private int sales;

public Star(String firstName, String lastName, String instrument, int sales) { this.firstName = firstName;

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new Star ("Abba", "John", "vocals", 12200);

Star aStar1 = new Star ("Elton", "John", "guitar", 20000);

Star aStar2 = new Star ("Debie", "Gission", "organ", 15000);

} }

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private String firstName;

private int sales;

this.lastName = lastName;

this.instrument = instrument;

this.sales = sales;

} public ??? incrementSales(???){

…this.firstName … …this.lastName … …this.instrument

…this.sales…

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private int sales;

this.sales = sales;

} public Star incrementSales(int sales){

return new Star(this.firstName, this.lastName, this.instrument, sales); }

}Immutable

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assertTrue(new Star ("Abba", "John", "vocals", 12200).incrementSales(20000) equals(new Star ("Abba", "John", "vocals",32200)));

assertTrue(aStar1.incrementSales(30000).equals(new Star ("Elton", "John", "guitar", 50000)));

assertTrueaStar2.incrementSales(20000).equals(new Star ("Debie", "Gission", "organ", 15000)));

}

Test incrementSales function

(define aStar1 (make-Star "Elton" "John" "Guitar" 20000))

(define aStar2 (make-Star "Debie" "Gission" "organ"

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Discuss more: equals method

• Q: Why we do not use Java built-in equals method?

• Our equals method:

public class Star {

private int sales;

…

public boolean equals(Object obj){

if (null == obj || ! (obj instanceof Star))

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mutableIncrementSales body

incrementSales methodpublic class Star {

private int sales;

this.sales = sales;

} public void setSales(int sales){

this.sales = sales ; }

}Mutable

Setter

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Discuss more: getSales method

Q: Do we use “selector” this.sales outside Star class

A: No

Solution: getSales method

public class Star {

private int sales;

public Star(String firstName, String lastName, String instrument, int sales) {

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public void testMutableIncrementSales (){

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+ int getSales()

Property or field

MethodData type

Class

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Exercise 2.3.3 (HTDP)

ticket, for example $5 Every performance costs the theater some money, for example $20 and plus service charge per attendee, for example $.50 Develop

produces how much income the attendees profit

Solution

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which computes the height that a rocket reaches in a given amount of time If

the rocket accelerates at a constant rate g, it reaches a speed of g · t in t time units and a height of 1/2 * v * t where v is the speed at t

Solution

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Re l a x…

& D o E x e rcise

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Student example

teacher.

teacher's name is equal to aTeacher and “none” otherwise.

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Class diagram

Student

+ String id + String firstName + String lastName + String teacher

+ ??? check(???) + ??? transfer(???)

Property or field

MethodData type

Class

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Define Class

Define classpublic class Student { private String id;

private String teacher;

}

Define structure

( (define-struct Student (id first last teacher))

Constructorpublic class Student { private String id;

public Student(String id, String firstName, String l astName, String teacher) { this.id = id;

(make-Student

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Test Student Constructor

(define aStudent1 (make-student “st2”

“Wilson” “Fillip” “Harper”)

(define aStudent2 (make-student “st3”

“Woops” “Helen” “Flatt”)

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public Student(String id, String firstName, String lastName, String teacher) { this.id = id;

}

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this.firstName = firstName;

this.teacher = teacher;

} public void transfer(String thatTeacher){

this.teacher = thatTeacher;

}

public String check(String thatTeacher){

if (this.teacher.equals(thatTeacher)) return this.lastName;

return "none";

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public void testCheck(){

assertEquals (new Student( "st1", "Find", "Matthew", "Fritz").check("Elise"),"none");

Student aStudent1 = new Student("st2", "Wilson", "Fillip", "Harper");

Student aStudent2 = new Student("st3", "Woops", "Helen", "Flatt");

assertEquals("none“, aStudent1.check("Lee"));

assertEquals("Helen“,aStudent2.check("Flatt"));

}

Test check function

(define aStudent1 (make-student “st2” “Wilson” “Fillip”

“Harper”)

(define aStudent2 (make-student “st3” “Woops” “Helen”

“Flatt”)

(string=? “none” (check (make-student “st1” “Find”

“Matthew” “Fritz”) “Elise”))

(string=? “none” (check aStudent1 “Lee”))

(string=? “Hellen” (check aStudent2 “Flatt”))

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}

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this.firstName = firstName;

this.teacher = teacher;

}

public Student transfer(String thatTeacher){

return new Student (this.id, this.firstName, this.lastName,thatTeacher);

}

Immutable

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public void testTransfer(){

assertTrue(new Student( "st1", "Find", "Matthew", "Fritz").tranfer("Elise") equals (new Student( "st1", "Find", "Matthew","Elise")));

assertTrue(aStudent1.tranfer("Lee").equals (new Student("st2", "Wilson",

Test transfer function

(define aStudent1 (make-student “st2” “Wilson” “Fillip”

(transfer aStudent1 “Lee” )

(transfer aStudent2 “Flister” )

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Discuss more: equals method

• Q: Why we do not use JUnit built-in equals method?

• Our equals method:

public class Student {

private String id;

public Student(String id, String firstName, String lastName, String teacher) {

…

public boolean equals(Object obj){

if (null == obj || ! (obj instanceof Student))

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transferMutable body

transfer methodpublic class Student { private String id;

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Discuss more: getTeacher method

Q: Do we use “selector” this.teacher outside Student class

A: No

Solution: getTeacher method

public class Student {

private String id;

public Student(String id, String firstName, String lastName, String teacher) {

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public void testMutableTransfer(){

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Class diagram

Student + String id

+ String firstName + String lastName + String teacher

+ String check(String thatTeacher) + Student transfer(String thatTeacher) + void mutableTransfer(String thatTeacher) + boolean equals(Student that)

+ String getTeacher()

Property or field

MethodData type

Class

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quadratic equation It then determines whether the equation is degenerate and,

if not, how many solutions the equation has The function produces one of four

symbols: 'degenerate, 'two, 'one, or 'none.

Solution

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Exercise 4.4.1 and 4.4.3 (HTDP)

• Information about the transaction in bank includes customer name, and deposit amount and maturity(computed in year)

• Develop the function interest It consumes a deposit amount and produces the actual amount of interest that the money earns

in a year The bank pays a flat 4% for deposits of up to $1,000, a flat 4.5% per year for deposits of up to $5,000, and a flat 5% for deposits of more than $5,000

• Some credit card companies pay back a small portion of the charges a customer makes over a year One company returns 25% for the first $500 of charges,

.50% for the next $1000 (that is, the portion between $500 and $1500),

75% for the next $1000 (that is, the portion between $1500 and $2500), and

1.0% for everything above $2500

Define the function payback , which consumes a charge amount and computes the corresponding pay-back amount.

SolutionSolution

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Prepare for next week

How to design class hierarchy

• I The Varieties of Data

• III Fun Methods

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Re l a x…

& D o E x e rcise

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Solution 2.3.3 (HTDP)

• Class definition

public class MovieTheatre {

private double ticketPrice;

private double costForPerformance;

private double costPerAttendee;

public MovieTheatre(double ticketPrice, double costForPerformance, double costPerAttendee) {

this.ticketPrice = ticketPrice;

this.costForPerformance = costForPerformance;

this.costPerAttendee = costPerAttendee;

}

public double cost(int numAttendee){

return this.costForPerformance + this.costPerAttendee * numAttendee;

}

public double revenue(int numAttendee){

return this.ticketPrice * numAttendee;

}

public double totalProfit(int numAttendee){

return this.revenue(numAttendee)- this.cost(numAttendee);

}

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