CSC108 Lecture #1 - Second verions of the Library program

CSC108 Lecture #1 - Second version of the Library program

The Book class: the first try

Here is the complete book class, before adding the constructor.

/**
 * Book models the behaviour of a book
 */
class Book {

    // instance variables
    private int numCopies;

    /**
     * sign out this book from the library
     */
    public void checkOut() {
        numCopies = numCopies - 1;
    }

    /**
     * buy copies for the collection
     * @param copies - the number of total copies purchased
     */
    public void buyCopies(int copies) {
        numCopies = copies;
    }

    /**
     * bring a book back to the library
     */
    public void checkIn() {
        numCopies = numCopies + 1;
    }

    /**
     * get number of copies available at this time
     * @return numCopies
     */
    public int numCopies() {
        return numCopies;
    }
}

Here is a sample main method that could be used to create a Book object and to call some methods on it.

// second version of the library program
// Notice that this is actually another class: Library will create
// Book objects.  The two classes work together.
public class Library {
    public static void main (String[] args) {

        // Declare a variable, ready to hold a reference to a Book object.
        Book b1;

        // Create a new Book object and save the reference to it in our
        // b1 variable
        b1 = new Book();  

        System.out.println ("Buy 5 copies of the book");
        b1.buyCopies(5);
        
        System.out.println ("Sign out a copy");
        b1.checkOut();

        System.out.println ("Sign out another copy");
        b1.checkOut();
   }
}