Dynamic object creation using input loops

Question

I have successfully completed, and no problems with the program, everything works just fine, except it does not show the the maximum and minimum price of the book. But, I do not want the program like this.

Currently the program consists of pre-defined array that consists of book name, that is, whenever a user enters input for a book, the program shows the book name and price of the book. So, I am thinking of something different, that is without pre-storing the book names and prices in the array.

Whatever name the user key-in for the book, that book name will be stored as an array along with the price. And the loop will be three times, that is after 1 input of book name and price, the user will again be prompted to enter book name, and last the the total number books and price will be displayed along with the maximum and minimum prices of the book, the user purchased.

Can anyone help me with this? Please see my coding below:

import java.util.Scanner;
public class BookStore {
    public static void main(String args[]){
        Scanner input = new Scanner(System.in);
        String[] books = {"Introduction To Java","Artificial Intlegence","Web Programming","Introduction To Database","English Speech","Introduction To C#"};

        double[] prices ={100,50,25,45,60,90}; 

        System.out.println("Welcome to SAJID's Book Shop");
        System.out.println();
        System.out.println("Please select the the book and write the number of the book :");
        System.out.println();
        System.out.println("1.Introduction To Java");
        System.out.println("2.Artificial Intlegence");
        System.out.println("3.Web Programming");
        System.out.println("4.Introduction To Database");
        System.out.println("5.English Speech");
        System.out.println("6.Introduction To C#");
        System.out.println();

        System.out.println("Total Number Of Books "+books.length);
        int totalBook;
        totalBook = books.length;

        double totalPrice=0;    
        int i=0;            
        while(i<=5){
            totalPrice+=prices[i];
            i++;
        }

        System.out.println("Total Price:$" + totalPrice);

        int bookTitle;
        System.out.print("Enter book Number: ");
        bookTitle = input.nextInt();

        if(bookTitle == 0){
            System.out.println("Book name: "+books[0]);
            System.out.print("Book price:$"+prices[0]);
            }

        if(bookTitle == 1){

            System.out.println("Book name: "+books[1]);
            System.out.print("Book price:$"+prices[1]);
        }
        if(bookTitle == 2){

            System.out.println("Book name: "+ books[2]);
            System.out.print("Book price:$"+prices[2]);
        }
        if(bookTitle == 3){

            System.out.println("Book name: "+books[3]);
            System.out.print("Book price:$"+prices[3]);
        }
        if(bookTitle == 4){

            System.out.println("Book name: "+books[4]);
            System.out.print("Book price:$"+prices[4]);
        }
        if(bookTitle == 5){

            System.out.println("Book name: "+books[5]);
            System.out.print("Book price:$"+prices[5]);
        }

        /*double min=0;
        for(i=0;i<books.length-1;i++){

            if(books[i] =< books[i++]){
                min=books[i];
                minBook = i;
            }*/
        }

        //System.out.print("Cheapest book: " + min);
    }       
 }

SimplyPanda · Accepted Answer · 2012-06-01 15:46:45Z

2

It's entirely possible I've misunderstood what you were asking, in which case, disregard everything below.

Currently, you're comparing the currently iterated book to the next book, and incrimenting i twice in the for loop. Try this:

double min = prices[i];
int minBook = 0;
for(int i = 1; i < books.length; i++) {
    if(prices[i] < min) {
        min = prices[i];
        minBook = i;
    }
}
System.out.print("Cheapest book: " + books[minBook]);

You can do something similar for maximums:

double max = prices[i];
int maxBook = 0;
for(int i = 1; i < books.length; i++) {
    if(prices[i] > max) {
        max = prices[i];
        maxBook = i;
    }
}

System.out.print("Cheapest book: " + books[maxBook]);

Of course, this assumes your list of books isn't empty.

edited Jun 1, 2012 at 15:46

answered Jun 1, 2012 at 15:41

SimplyPanda

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3 Comments

bleach64 Over a year ago

I was stuck in finding the maximum and minimum cost of the book and this post solved my max and min problem. Thanks again

bleach64 Over a year ago

can u help me with one more thing, that is, I dont want to use predefined array, I want to use undefined array for this program. That is whenever a user inputs the name of the book. That name will be stored as an array and display the book name, total pirce and total number of books that are entered

SimplyPanda Over a year ago

Since arrays are intrinsically sized (you set their sizes at declaration) it would probably be better to use something like a LinkedList or ArrayList. You'll probably need a do-while loop that exits on user request to allow the user to enter all of that information.

Lilienthal · Accepted Answer · 2012-06-01 17:12:19Z

Because you're using dynamic inputs, you can end up with any number of books, which is why you should not use arrays anymore. Their size cannot easily be changed so I suggest you change to ArrayList instead.

Furthermore, because your books and prices array are closely related, you may want to create your own Book object to store this information. For example:

public class Book {
    String title;
    double price;
    public Book(String title, double price) {
        this.title = title;
        this.price = price;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
}

To make the whole thing dynamic, you essentially require a rewrite of most of your code, which I've done below. I'm not sure if I made a homework assignment here, but if I am, I strongly suggest that you read through the entire code to understand what it does.

Scanner input = new Scanner(System.in);
List<Book> books = new ArrayList<Book>();
boolean done = false;

System.out.println("Welcome to SAJID's Book Shop\n");
// Now the user can input some books.
String title;
double price;
while (!done) {
    System.out.println("Enter a book title (nothing to stop): ");
    title = input.nextLine();
    if (title.isEmpty()) {
        // User didn't enter a title, stop this loop.
        done = true;
    }
    else {
        System.out.println("Enter a price: ");
        price = input.nextDouble();
        // Because nextDouble() only reads the next number and doesn't finish the entire line, we have to manually go to the next line.
        input.nextLine(); 
        // Create a new book and add it to our shop.
        Book newBook = new Book(title, price);
        books.add(newBook);
    }
}

System.out.println("The following books are for sale:");
for (int i = 0; i < books.size(); i++) {
    // Remember that the first book in our list is number 0, not 1, so we add 1 to i.
    System.out.println((i + 1) + ". - " + books.get(i).title);
}
System.out.println("Total Number Of Books "+ books.size());

// Now buy some books.
List<Book> purchasedBooks = new ArrayList<Book>();
done = false;
String line;
int bookNumber;
while (!done) {
    System.out.println("Enter the number of a book you'd like to buy (0 to stop): ");
    bookNumber = input.nextInt();
    input.nextLine();
    if (bookNumber == 0) {
        // We stop if the user enters 0.
        done = true;
    }
    else {
        // Remember that the first book in our list is number 0, not 1.
        purchasedBooks.add(books.get(bookNumber - 1));
    }
}

System.out.println("You're buying these books:");
double totalPrice = 0;
for (int i = 0; i < purchasedBooks.size(); i++) {
    // Remember that the first book in our list is number 0, not 1, so we add 1 to i.
    System.out.println((i + 1) + ". - " + purchasedBooks.get(i).price + " - " + purchasedBooks.get(i).title);
    totalPrice += purchasedBooks.get(i).price;
}
System.out.println("Total Number Of Books Bought: " + purchasedBooks.size());
System.out.println("Total Price: " + totalPrice);

// Find the cheapest and the most expensive book.
Book minBook = purchasedBooks.get(0);
Book maxBook = purchasedBooks.get(0);
// Iterate over our books using a foreach loop.
for (Book book : purchasedBooks) {
    if (book.price < minBook.price) {
        minBook = book;
    }
    else if (book.price > maxBook.price) {
        maxBook = book;
    }
}
System.out.println("Cheapest Book: " + minBook.title + " (" + minBook.price + ")");
System.out.println("Most Expensive Book: " + maxBook.title + " (" + maxBook.price + ")");

assylias · Accepted Answer · 2012-06-01 15:36:22Z

1

That probably does not your question (which I have not really understood) but this is too long for a comment. You could start by replacing all your ifs by:

if(bookTitle >= 0 && bookTitle <= 5){
    System.out.println("Book name: "+books[bookTitle]);
    System.out.print("Book price:$"+prices[bookTitle]);
}

answered Jun 1, 2012 at 15:36

assylias

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4 Comments

bleach64 Over a year ago

But it gives an error..says ... "reached end of the file while parsing"

assylias Over a year ago

When you run the program or when you try to compile it?

assylias Over a year ago

Have you counted the opening and closing { and }? In your example, there is one } more than { (the extra one is after the commented for loop at the bottom of your code, which should be inside the comment section).

bleach64 Over a year ago

it works.. compiles great.. the curly braces was the main problem

ChadNC · Accepted Answer · 2012-06-01 16:12:10Z

I posted it a little late but here you go. I got rid of all thos if statements and used a switch, sorted your prices array and changed some of your looping. EDIT oops! I messed up. You wanted the cheapest book not the cheapest book price which is what I did.

        Scanner input = new Scanner(System.in);
    String[] books = {"Introduction To Java","Artificial Intlegence","Web Programming","Introduction To Database","English Speech","Introduction To C#"};

    double[] prices ={100,50,25,45,60,90};

    System.out.println("Welcome to SAJID's Book Shop");
    System.out.println();
    System.out.println("Please select the the book and write the number of the book :");
    System.out.println();
    System.out.println("1.Introduction To Java");
    System.out.println("2.Artificial Intlegence");
    System.out.println("3.Web Programming");
    System.out.println("4.Introduction To Database");
    System.out.println("5.English Speech");
    System.out.println("6.Introduction To C#");
    System.out.println();

    System.out.println("Total Number Of Books "+books.length); 

    double totalPrice=0;
    for(int i = 0; i<=5; i++){
        totalPrice+=prices[i];
    }

    System.out.println("Total Price:$" + totalPrice);

    System.out.print("Enter book Number: ");

    int bookTitle = input.nextInt();
    switch(bookTitle){
      case 1:
        System.out.println("Book name: "+books[0]);
        System.out.println("Book price:$"+prices[0]);
        break;
      case 2:
        System.out.println("Book name: "+books[1]);
        System.out.println("Book price:$"+prices[1]);
        break;
      case 3:
        System.out.println("Book name: "+ books[2]);
        System.out.println("Book price:$"+prices[2]);
        break;
      case 4:
        System.out.println("Book name: "+books[3]);
        System.out.println("Book price:$"+prices[3]);
        break;
      case 5:
        System.out.println("Book name: "+books[4]);
        System.out.println("Book price:$"+prices[4]);
        break;
      default:// since there are only 5 books use #6 as default
        System.out.println("Book name: "+books[5]);
        System.out.println("Book price:$"+prices[5]);
        break;
  }

    // assuming the prices array holds the price of each individual book
    // sort the prices array
    java.util.Arrays.sort(prices);
    System.out.println("Cheapest book: " + prices[0]);
    System.exit(0);

}

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