How to do this? (Java)

Question

Composition

There are two ways to reuse existing classes, namely, composition and inheritance.

With composition (aka aggregation), you define a new class, which is composed of existing

classes. With inheritance, you derive a new class based on an existing class, with modifications or

extensions.

A class called Author is designed as shown in the class diagram. It contains:

name: String

email:String

gender: char--->'m' or'f'

Methods:

+Author (name : String, email : String,

gender: char)

Methods:

+getName():String

+get Email():String

+set Emaill(email: String) : void

+getGender (): char

+toString ():String--->"name (gender) at email"

● Three private member variables: name (String), email (String), and gender (char of

either 'm' or 'f' - you might also use a boolean variable called isMale having value

of true or false).

●A constructor to initialize the name, email and gender with the given values.

(There is no default constructor, as there is no default value for name, email and gender.)

●Public getters/setters: getName(), getEmail(), setEmail(), and getGender().

(There are no setters for name and gender, as these properties are not designed to be

changed.)

●A toString() method that returns "name (gender) at email", e.g., "Tan Ah Teck (m) at

[email protected]".

A Book is written by one Author - Using an "Object" Member Variable

Book: Author:

-name: String --name:String

-author: Author -------(1)-----> --email:StrinE

-price: double --gender: char

-qty: int

Methods:

+Book(name: String, author: Author,

price: double, qty: int)

+getName () : String

+getAuthor () :Author

+getPrice(): double

+setPrice (price: double) : void

+getQty(): int

+setQty (qty: int) : void

+toString(): String--->" 'book-name' by author-name (gender) at email"

■Let's design a Book class. Assume that a book is written by one (and exactly one) author. The

Book class (as shown in the class diagram) contains the following members:

●Four private member variables: name (String), author (an instance of the Author class we

have just created, assuming that each book has exactly one author), price (double),

and qty (int).

●The public getters and

setters: getName(), getAuthor(), getPrice(), setPrice(), getQty(), setQty().

●A toString() that returns "'book-name' by author-name (gender) at email". You could reuse

the Author's toString() method, which returns "author-name (gender) at email".

Answer 1

//********* Author.java ****************//

class Author

{

private String name;

private String email;

private boolean gender; //male=false; female=true;

public Author( String name, String email, boolean gender)

{

this.name = new String(name);

this.email = new String(email);

this.gender = gender;

}

public String getName() { return(name); }

public String getEmail() { return(email); }

public boolean getGender() { return(gender); }

public Author(Author author)

{

this.name = new String(author.getName());

this.email = new String(author.getEmail());

this.gender = author.getGender();

}

public void setName( String name) { this.name = new String(name); }

public void setEmail(String email) { this.email = new String(email); }

public void setGenderMale() { this.gender = false; }

public void setGenderFemale() { this.gender = true; }

@Override public String toString()

{

char chGender = (this.gender) ? 'F' : 'M';

return(

new String(

this.name + "(" + chGender + ") at " + this.email

)

);

}

}

//******** Book.java ***********************//

class Book

{

private String title;

private Author author;

private double price;

private int qty;

Book( String title, Author author, double price, int qty)

{

this.title = new String(title);

this.author = new Author(author);

this.price = price;

this.qty = qty;

}

public String getTitle() { return(title); }

public Author getAuthor() { return new Author(this.author); }

public double getPrice() { return(price); }

public int getQty() { return(qty); }

Book( Book book)

{

this.title = book.getTitle();

this.author = new Author( book.getAuthor());

this.price = book.getPrice();

this.qty = book.getQty();

}

public void setPrice(double price) { this.price = price; }

public void setQty( int qty) { this.qty = qty; }

@Override public String toString()

{

return(

new String(

"book title:" + this.title + " by Author " + this.author.toString() +

" price = " + this.price + " : qty = " + this.qty

)

);

}

}

//**** main ************//

class LaviMain

{

public void Go()

{

Author author = new Author("Patrick Baldwin","[email protected]",false);

Book book = new Book("How to create nested objects in Java",author,42.35,10);

System.out.println(book.toString());

}

public static void main(String args[])

{

LaviMain x = new LaviMain();

x.Go();

}

}