JAVA LAB 3

class Book {
    public String bookTitle = "Jaava";
    public String author = "idk";
    public String ISBN = "idk";
    public int numCopies = 0;

    public Book(String name, String auth, String isbn, int x) {
        bookTitle = name;
        author = auth;
        ISBN = isbn;
        numCopies = x;
    }
}

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import java.util.Scanner;

class BookStore {
    private Book[] b = new Book[10];
    int len = 0;

    public BookStore() {

        b = new Book[10];
        b[0] = new Book("Java", "JAuth", "JIsbn", 3);
        b[1] = new Book("C", "c-auth", "c-isbn", 4);
        b[2] = new Book("Python", "PyAuth", "PyIsbn", 5);

                                                 len = 3;

    }

    public void display() {

        System.out.println("\n");

        // find the total num of books in array and print one by one

        for (int i = 0; i < 10 && b[i] != null; i++) {
            System.out.printf("%d %s\t%s\t%s\t%d\n", i+1, b[i].bookTitle,
                              b[i].author, b[i].ISBN, b[i].numCopies);
        }

        // if there are no books
        if (len == 0)  System.out.println("There are no books to display.");

        System.out.println("\n\n");
    }

    public void order(String isbn, int nums) {
        int index = 0;
        for (; index < len && b[index] != null; index++) {
            // if the book exists in the book shop
            if (b[index].ISBN.equals(isbn) ) {
                b[index].numCopies += nums;

                // GET OUT OF METHOD
                return;
            }
        }

        // if the method came here, it means the book does not exist
         Scanner scan = new Scanner(System.in);

         System.out.println("New Book Name: ");
         String name = scan.nextLine();

         System.out.println("New Book's Author: ");
         String auth = scan.nextLine();


        b[index] = new Book(name, auth, isbn, nums);
                                              len++;
    }

    public void sell(String name, int nums) {
        int index = 0;
        for (; index < len && b[index] != null; index++) {

            // if the book exists in the book shop
            if (b[index].bookTitle.equals(name) ) {

                if (b[index].numCopies >= nums) {

                    b[index].numCopies -= nums;

                    System.out.printf("You have just sold %d copies of %s\n\n", nums, name);
                    System.out.printf("You now have %d of %s left.\n\n", b[index].numCopies, b[index].bookTitle);

                    // GET OUT OF METHOD
                    return;
                }
            }
        }
        System.out.println("The book is not available now... Do check back another time!");
    }

}
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import java.util.Scanner;

class BookStoreApp {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);


        BookStore books = new BookStore();

        System.out.println("\n---------- Welcome to your Book Store App ----------\n\n");

        while (true) {

            System.out.println("Enter <1> for Displaying all books.");
            System.out.println("Enter <2> to order a new book.");
            System.out.println("Enter <3> for selling a book.");
            System.out.println("Enter <4> for Exiting Out.\n\n");
            System.out.printf("Enter your choice: ");

            int choice;
            choice = scan.nextInt();

            String nameOrIsbn;
            int nums;

            switch (choice)
            {
                case 1:
                    books.display(); break;
                case 2:
                    System.out.printf("Enter Book's ISBN: ");  nameOrIsbn = scan.next();
                    System.out.printf("How many? ");  nums = scan.nextInt();
                    books.order(nameOrIsbn, nums);
                    break;
                case 3:
                    System.out.printf("Enter Book's Name: ");  nameOrIsbn = scan.next();
                    System.out.printf("How many? ");  nums = scan.nextInt();
                    books.sell(nameOrIsbn, nums);
                    break;
                case 4:
                    System.out.println("Bye Bye!\nSee you later!");  scan.close();
                    System.exit(1);
                    break;

                default:
                    System.out.println("Only numbers between 1 and 4 (inclusive) are accepted.\n\n");
            }
        }

    }
}