Methods with effects (lập TRÌNH cơ bản SLIDE)

class ALoBookspublic abstract class ALoBooks { public abstract ALoBooks addBook book; }... • The list of stations is: Kenmore, Park, Center, North, Science, Ashmont, Downtown, Charles, S

Methods with effects

Week 14,15

A2 Programming Course

Cyclical Data

Bookstore Manager’s Problem

A Variation of the Bookstore Manager’s

Problem

• Develop a program that assists a bookstore

manager The manager's program should keep a record for each book

• The record must include information about the author, the book's title, its price, and its

publication year

• The information about the author includes

author's name, year of birth, and a list of books written by this author

• Note: Remember to implement toString()

• The bookstore has the following books written by Jack London, born 1876:

– Call of the Wild (1903), published in 1995, $10

– The Sea-Wolf (1904), published in 1999, $12

– Martin Eden (1913), published in 1998, $12

– White Fang (1906), published in 2001, $10

• The bookstore has the following books written by

Danielle Steel, born in 1955, all in their original edition:

Problem in Designing Constructors

• To create a new object in the class Book we need

to refer to the Author But each Author refers to a list of books

• Q: The egg comes first or the hen comes first?

• Solution: A reasonable solution is to define an

Author object with an empty list of books Then,

as the author writes a new book, we create a Book

add this book to the author's list of books

public class AuthorTest extends TestCase {

public void test() {

Author jackLondon = new Author("Jack London", 1876);

Book cotw = new Book(jackLondon, "Call of the Wild", 1995, 10);Book tsw = new Book(jackLondon, "The Sea-Wolf", 1999, 12);Book me = new Book(jackLondon, "Martin Eden", 1998, 12);

Book wf = new Book(jackLondon, "White Fang", 2001, 10);

System.out.println(jackLondon);

Author danielleSteel = new Author("Danielle Steel", 1955);

Book d = new Book(danielleSteel, "Daddy", 1989, 20);

Book h = new Book(danielleSteel, "Heartbeat", 1992, 15);

Book j = new Book(danielleSteel, "Jewels", 1993, 22);

Book w = new Book(danielleSteel, "Wings", 1995, 25);

Book tg = new Book(danielleSteel, "The Ghost", 1995, 28);

System.out.println(danielleSteel);

}

}

public class Author {

private String name;

private int birthYear;

private ALoBooks books;

public Author(String name, int birthYear) {

public String toString() {

return this.name + ", " + this.birthYear + "\n" + this.books;}

}

public class Book {

private Author author;

private String title;

private double cost;

private int publishYear;

public Book(Author author, String title, int publishYear, double cost) {

public String toString() {

return this.author.getName() + ", " + this.title + ", " +

this.cost + ", " + this.publishYear + "\n";

}

}

addBook() in Author

// class Author

void addBook(Book book) {

this.books = this.books.add(book); }

class ALoBooks

public abstract class ALoBooks {

public abstract ALoBooks add(Book book); }

class Empty

public class Empty extends ALoBooks {

public ALoBooks add(Book book) {

Class Cons

public class Cons extends ALoBooks {

private Book first;

private ALoBooks rest;

public Cons(Book first, ALoBooks rest) {

this.first = first;

this.rest = rest;

}

public ALoBooks add(Book book) {

return new Cons (book, this);

}

public String toString() {

return this.first + " " + this.rest;

}

}

New add(Book book) version

public abstract class ALoBooks {

public ALoBooks add(Book book){

}

}

The Transportation Network

Problem

Problem Statement

• The Metropolitan Transit Agency has a web

site that allows the user to display information about any of its stations and its train routes

• The list of stations is: Kenmore, Park, Center, North, Science, Ashmont, Downtown, Charles, State, Bowdoin, Maverick, Wonderland

Center, North to Science

• Red Line runs from Ashmont through

Downtown and Park to Charles

State, Maverick, to Wonderland

Kenmore Park Center North

Ashmont Downtown State Maverick Wonderland

Charles Bowdoin

Science

The Problem

• The class Station needs to have fields for its

• The class Route needs to have a field for its name, the origin, the destination, and for a

list of stations

• Again, we cannot build a route without

knowing all the stations, but the station

should know what routes it serves

• Then, create the route object, and instruct the

serves this route , as well as the origin and

destination station

11 stations

ConsLoStations

- Station first

- ALoStations rest

11 rest

2 11

first

A Simpler Class Diagram

public class RouteTest extends TestCase {

public void test() {

// create stations for green route

Station kentmore = new Station("Kentmore"); Station park = new Station("Park");

Station center = new Station("Center");Station north = new Station("North");

Station science = new Station("Science");

// create green route

Route green = new Route("Green", kentmore, science);

green.addStation(park); green.addStation(center);

green.addStation(north); System.out.println(green);

// create stations for red route

Station ashmont = new Station("Ashmont"); Station charles = new Station("Charles");

Station downtown = new Station("Downtown");

// create red route

Route red = new Route("Red", ashmont, charles);

red.addStation(downtown); red.addStation(park);

System.out.println(red);

// create stations for blue route

Station bowdoin = new Station("Bowdoin"); Station state = new Station("State");

Station maverick = new Station("Maverick"); Station wonderland = new Station("Wonderland"); // create blue route

Route blue = new Route("Blue", bowdoin, wonderland);

public class Station {

private String name;

private ALoRoutes routes;

public Station(String name) {

public String toString() {

return "Station " + this.name + ": " + this.routes.getName();}

}

public class Route {

private String name;

private Station origin;

private Station destination;

private ALoStations stations;

public Route(String name, Station origin, Station destination) {

public String toString() {

return "Route " + this.name + ": " + this.stations;

}

}

addRoute() in Station

// class Station

void addRoute(Route route) {

this.routes = new ConsLoRoutes(route, this.routes); }

addStation() in Route

Q: How can we add a Station to a Route?

//class Route

this.stations = new ConsLoStations(station, this.stations);

}

Class ALoRoutes

public abstract class ALoRoutes {

public abstract String getNames(); }

class ConsLoRoutes

public class ConsLoRoutes extends ALoRoutes {

private Route first;

private ALoRoutes rest;

public ConsLoRoutes(Route first, ALoRoutes rest) {

this.first = first;

this.rest = rest;

}

public String getNames() {

return this.first.getName() + " " + this.rest.getNames();}

}

class ALoStations

public abstract class ALoStations { }

class ConsLoStations

public class ConsLoStations extends ALoStations {

private Station first;

private ALoStations rest;

public ConsLoStations(Station first, ALoStations rest) {

this.first = first;

this.rest = rest;

}

public String toString() {

return this.first.getName() + " " + this.rest;

}

}

• Compare with another implementation in book “ How to design class hierarchies”

The University Registrar Problem

Problem Statement

• In the university registrar's database there is a list of course sections offered this term

• For each course section, the registrar records the

students enrolled in the course

• The information about each student includes the

name, an id number, and student's schedule

taking this term

• The university offers the following courses this term:

– Math course, 4 credits

– Physics course, 5 credits

– Biology course, 5 credits

– Music course, 2 credits

The Problem

• The problem we need to face is how to

include a list of students in the object that

represents one course, and, at the same time, include student's schedule in the object that represents a student

11 courses

ConsLoCourses

- Course first

- ALoCourse rest

11 rest

public class CourseTest extends TestCase {

public void test() {

// create courses

Course math = new Course("Math", 4); Course physics = new Course("Physics", 5); Course biology = new Course("Biology", 5); Course music = new Course("Music", 2);

// create student Jenna

Student jenna = new Student(1123, "Jenna");

jenna.addCourse(math); jenna.addCourse(physics);

jenna.addCourse(biology); System.out.println(jenna);

// create student John

Student john = new Student(1345, "John");

john.addCourse(biology); john.addCourse(music);

john.addCourse(physics); System.out.println(john);

// create student Ernie

Student ernie = new Student(4323, "Ernie");

ernie.addCourse(biology); ernie.addCourse(music);

System.out.println(ernie);

// create student Ernie

Student rob = new Student(3213, "Rob");

public class Course {

private String name;

private int credits;

private ALoStudents students;

public Course(String name, int credits) {

public String toString(){

return this.name+ ", "+this.credits+", cac sinh vien theo hoc:"+

this.students;

}

}

public class Student {

private int id;

private String name;

private ALoCourses courses;

public Student(int id, String name ) {

public String toString(){

return this.id+ "-"+ this.name+",cac mon dang ky:"+this.courses.getNames();

}

}

public void addStudent(Student student) {

this.students = new ConsLoStudents(student, this.students);

}

class ALoStudents

public abstract class ALoStudents { public abstract String getNames(); }

class ConsLoStudents

public class ConsLoStudents extends ALoStudents {

private Student first;

private ALoStudents rest;

public ConsLoStudents(Student first, ALoStudents rest) {

this.first = first;

this.rest = rest;

}

public String getNames() {

return this.first.getName() + " " + this.rest.getNames();}

}

class ALoCourses

public abstract class ALoCourses { public abstract String getNames(); }

class ConsLoCourses

public class ConsLoCourses extends ALoCourses {

private Course first;

private ALoCourses rest;

public ConsLoCourses(Course first, ALoCourses rest) {

this.first = first;

this.rest = rest;

}

public String getNames() {

return this.first.getName() + " " + this.rest.getNames();}

}

Exercises

Exercise 2.1.1

• Develop the data definition for classes that

represent employees and their project groups Each employee (identified by a name and year

of birth) belongs to one or more project

groups, and may be a leader of one or more groups Each group has a name, one leader,

and a list of employees in the group

Exercise 2.1.2

• Develop the data definition for classes that represent the teams in the town youth baseball league League has a list of teams and a list of coaches Each team has a name, a coach, a list of players, and the current record of wins and losses A coach may coach more than one team For each coach we record the name, phone number, and coach's teams For each player

we need to know the name, year of birth, and the

team Player can be on only one team