cart.java

这是一个网上书站的例子

package com.cart;

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;

public class Cart {
	private HashMap items;
	private int itemCount;
	public Cart()
	{
		itemCount=0;
		items=new HashMap();
	}
	public synchronized Collection getAll()
	{
		return items.values();
	}
	public synchronized void clear()
	{
		itemCount=0;
		items.clear();
	}
	public synchronized void remove(String bookid)
	{
		items.remove(bookid);
		itemCount=itemCount-1;
	}
	public synchronized float getTotalValue()
	{
		float total=0.0f;
		Collection c=getAll();
		for(Iterator it=c.iterator();it.hasNext();)
		{
			BookItem bookitem=(BookItem)it.next();
			Book book=bookitem.getBook();
			total+=book.getAgio()*book.getPrice()*bookitem.getAmount();
		}
		return total;
	}
	public synchronized float getSaveValue()
	{
		float totalsave=0.0f;
		Collection c=getAll();
		for(Iterator it=c.iterator();it.hasNext();)
		{
			BookItem bookitem=(BookItem)it.next();
			Book book=bookitem.getBook();
			totalsave+=(1.0f-book.getAgio())*book.getPrice()*bookitem.getAmount();
		}
		return totalsave;
	}
	public synchronized void add(String bookid,Book book,int num)
	{
		if(items.containsKey(bookid))
		{
			BookItem bookitem=(BookItem)items.get(bookid);
			int oldcount=bookitem.getAmount();
			int newcount=oldcount+num;
			items.remove(bookid);
			bookitem=new BookItem(book,newcount);
			
			items.put(bookid, bookitem);
		}
		else
		{
			BookItem bookitem=new BookItem(book,num);
			items.put(bookid,bookitem);
			itemCount++;
		}
	}
	public int getItemCount() {
		return itemCount;
	}
	public static void main(String args[])
	{
		Book book1=new Book("zxf",20.0f,0.5f,"zxf","zxf","zxf","zxf");
		Book book2=new Book("zxf",30.0f,0.5f,"zxf","zxf","zxf","zxf");
		Book book3=new Book("zxf",40.0f,0.5f,"zxf","zxf","zxf","zxf");
		Cart cart=new Cart();
		cart.add("1", book1, 1);
		cart.add("1", book1, 2);
		cart.add("2", book2, 1);
		System.out.println(cart.getItemCount());
		System.out.println(cart.getSaveValue());
		
		
	}
	
	
	

}