shoppingcart.java

一个网上书店的例子

package myshop;

import java.util.*;

/** A shopping cart data structure used to track orders.
 *  The OrderPage servlet associates one of these carts
 *  with each user session.
 *  <P>
 *  Taken from Core Servlets and JavaServer Pages 2nd Edition
 *  from Prentice Hall and Sun Microsystems Press,
 *  http://www.coreservlets.com/.
 *  &copy; 2003 Marty Hall; may be freely used or adapted.
 */
 
public class ShoppingCart {
  private ArrayList itemsOrdered;

  /** Builds an empty shopping cart. */
  
  public ShoppingCart() {
    itemsOrdered = new ArrayList();
  }
  
  public List getItemsOrdered() {
    return(itemsOrdered);
  }

  
  public synchronized void addItem(String id,String sort) {
    ItemOrder order;
    for(int i=0; i<itemsOrdered.size(); i++) {
      order = (ItemOrder)itemsOrdered.get(i);
      if (order.getBookId().equals(id)) {
        order.incrementNumItems();
        return;
      }
    }
    ItemOrder newOrder = new ItemOrder(id,sort);
    itemsOrdered.add(newOrder);
  }

  
  public synchronized void setNumOrdered(String id,int numOrdered){
    ItemOrder order;
    for(int i=0; i<itemsOrdered.size(); i++) {
      order = (ItemOrder)itemsOrdered.get(i);
      if (order.getBookId().equals(id)) {
        if (numOrdered <= 0) {
          itemsOrdered.remove(i);
        } else {
          order.setNumItems(numOrdered);
        }
        return;
      }
    }
  }
  
}