librarybasket.java

关于sqlserver图书管理的说明性文档

package library;
import java.util.*;
import java.io.*;
import java.text.*;

/**
 * Class <b>LibraryBasket</b> contains
 * the specification of a JaveBean modeling
 * a basket at a library.
 *
 * @author CTE
 * @version 1.0
 */

public class LibraryBasket
{
    int MAXBOOKS = 100;

    /**
     * The Book hashtable stores all of the books in the 
     * library basket.  The key is the book isbn, the value 
     * stored is the quantity of that book. Initially, the 
     * Book hashtable has a size of 15 and a load factor of .75.
    */
    
    Hashtable Books = new Hashtable( 15, (float) .75 );
    int numBooks=0;
    
    /**
     * Empty constructor.  All JavaBeans must have an empty constructor.
     * The student is not repsonsible for adding any code to this function.
     */
    public LibraryBasket()
    {}

    /**
     * Remove an item from the library basket.
     * @param ISBN String input isbn to remove
     * @return void
     */
    public void removeItem( String ISBN )
    {
	Integer Quantity;

	//get the quantity of the book from the hash table.

	Quantity = (Integer) Books.get( ISBN );

	//a null quantity means that no book with this ISBN is in the hashtable

	if (Quantity==null)
	    { 
		return;
	    }

	/**
	 * If there is only one copy of this particular book in the hash table, remove
	 * the entry totally from the hash table.
	 */
	if (Quantity.intValue()==1)
	    {
		Books.remove( ISBN );
		numBooks--;
	    }
	/**
	 * If the quantity of this ISBN is greater than 1, 
	 * decrement the quantity and place the
	 * new quanity back into the hashtable.
	 */
	else
	    {
		int tempQuant = Quantity.intValue();
		tempQuant--;
		Books.remove( ISBN );
		Books.put( ISBN, new Integer(tempQuant) );
	    }
    }
	
    /**
     * Add an item to the library basket.
     * @param ISBN String isbn of item to add
     * @return void
     */
    public void addItem( String ISBN )
    {
	Integer Quantity;
	// Get the quantity for this book in the basket.
	Quantity = (Integer) Books.get( ISBN );
	/**
	 * If the quantity is null, then this book is not in the basket, so
	 * add it to the hashtable.
	 */
	if (Quantity==null)
	    {
		Quantity = new Integer(1);
		Books.put( ISBN, Quantity );
		numBooks++;
	    }
	/**
	 * If the book is in the basket, remove the entry
	 * from the hash table and place the newly incremented 
	 * quantity in back into the basket.
	 */
	else
	    {
		int tempQuant = Quantity.intValue();
		tempQuant++;
		Books.remove( ISBN );
		Books.put( ISBN, new Integer(tempQuant) );
	    }
    }

    /**
     * Return the number of distinct books in the basket.
     * @return int
     */
    public int getnumBooks()
    {
	return numBooks;
    }

    /**
     * Get the total number of books in the basket for a given ISBN.
     * @param ISBN String isbn of book
     * @return int
     */
    public int getQuantity( String ISBN )
    {
	Integer Quantity;
	Quantity = (Integer) Books.get( ISBN );
	if (Quantity==null)
	    return 0;
	else
	    return Quantity.intValue();
    }

    /**
     * Return an array of strings which are all of the distinct isbns in the basket.
     * @return String[]
     */
    public String [] getBooks()
    {
	String [] returnISBNs = new String[MAXBOOKS];
	int currPos = 0;
	for( Enumeration bookEnumeration = Books.keys(); bookEnumeration.hasMoreElements(); )
	    {
		returnISBNs[currPos] = (String) bookEnumeration.nextElement();
		currPos++;
	    }
	return returnISBNs;
    }
}