cart.java

购物车模块实例。购物车模块可以浏览商品类别；可以根据商品类别浏览商品信息；可以购买商品；可以查看购物车的商品；可以修改购买商品的数量和删除购买的商品。

package data;

import java.util.*;

public class Cart {
  private Hashtable goods = new Hashtable();
  private String customer = "";

  //Cart类的构造器
  public Cart() {}
  //添加商品的方法
  public void addGoods(Hashtable goods){
    //取得添加商品的ID集合
    Enumeration newGoodsIds = goods.keys();
    while(newGoodsIds.hasMoreElements()){
       Object goodsId = newGoodsIds.nextElement();
      //购买车的商品包括新添加商品
      if(this.goods.containsKey(goodsId)){
        //分解添加商品字符串
        String[] newGoods = decodeGoodsStr(goods.get(goodsId).toString());
        //分解购物车商品字符串
        String[] oriGoods = decodeGoodsStr(this.goods.get(goodsId).toString());
        //增加商品数量
        int newQuantity = Integer.parseInt(newGoods[3]) +
            Integer.parseInt(oriGoods[3]);
        //将修改后的商品数量放入购物车的商品集合，覆盖原来的商品记录
        this.goods.put(goodsId, newGoods[0] + "@@" + newGoods[1] + "@@"
                       + newGoods[2] + "@@" + String.valueOf(newQuantity));
      //购买车的商品不包括新添加商品
      }else{
        this.goods.put(goodsId, goods.get(goodsId));
      }
    }
  }
  //修改商品数量的方法
  public void updateGoods(Hashtable goods){
    //取得修改商品的ID集合
    Enumeration newGoodsIds = goods.keys();
    while(newGoodsIds.hasMoreElements()){
      Object goodsId = newGoodsIds.nextElement();
      //覆盖购物车的商品记录
      this.goods.put(goodsId, goods.get(goodsId));
    }
  }
  //删除商品数量的方法
  public void removeGoods(java.util.Collection goodsId){
    java.util.Iterator goodsIdIterator = goodsId.iterator();
    while(goodsIdIterator.hasNext()){
      //删除购物车的商品记录
      this.goods.remove(goodsIdIterator.next());
    }
  }
  //分解商品字符串的方法
  public String[] decodeGoodsStr(String goodStr){
    //通过StringTokenizer类分解商品字符串
    StringTokenizer goodsTokenizer = new StringTokenizer(goodStr, "@@");
    String[] goods = new String[4];
    int i = 0;
    //将分解后的商品信息放入数组，分别是产品名称、单位数量、单价和购买数量
    while(goodsTokenizer.hasMoreTokens()){
      goods[i] = goodsTokenizer.nextToken();
      i++;
    }
    return goods;
  }
  //取得顾客名字的方法
  public String getCustomer() {
    return customer;
  }
  //设置顾客名字的方法
  public void setCustomer(String customer) {
    this.customer = customer;
  }
  //取得购物车商品集合类的方法
  public Hashtable getGoods() {
    return goods;
  }

  //显示商品的方法
  public Object[][] getGoodsobjs(){
    Enumeration GoodsIds = goods.keys();
    //创建商品数组
    Object[][] goodsObjs = new Object[goods.size()+1][7];
    //创建单个商品数组
    String[] oneGoodsStrs = new String[4];
    int row = 0;
    String goodsStr = "";
    String goodsId = "";
    double amount = 0;
    double oneGoodAmount = 0;
    int quantity = 0;
    while(GoodsIds.hasMoreElements()){
      //取得商品标识
      goodsId = (String)GoodsIds.nextElement();
      //取得商品字符串
      goodsStr = (String)goods.get(goodsId);
      //分解商品字符串
      oneGoodsStrs = decodeGoodsStr(goodsStr);
      goodsObjs[row][0] = goodsId;                         //取得商品标识
      goodsObjs[row][1] = oneGoodsStrs[0];                 //取得商品名称
      goodsObjs[row][2] = oneGoodsStrs[1];                 //取得单位数量
      goodsObjs[row][3] = new Double(oneGoodsStrs[2]);     //取得单价
      goodsObjs[row][4] = new Boolean(false);  //是否修改
      goodsObjs[row][5] = new Integer(oneGoodsStrs[3]);    //取得购买数量
      try{
        oneGoodAmount = Double.parseDouble(oneGoodsStrs[2]) *
            Double.parseDouble(oneGoodsStrs[3]);
        quantity += Integer.parseInt(oneGoodsStrs[3]);       //累加购买数量
      }catch(Exception ex){
        oneGoodAmount = 0;
      }
      //累加总金额
      amount += oneGoodAmount;
      goodsObjs[row][6] = new Double(oneGoodAmount);  //取得金额
      row++;
    }
    //在最后一行显示总金额
    goodsObjs[row][0] = "总金额";
    goodsObjs[row][1] = "";
    goodsObjs[row][2] = "";
    double averagePrice = 0;
    //计算平均单价
    if(quantity != 0){
      averagePrice = Math.round((amount/quantity)*100);
      averagePrice /= 100;
    }else{
      averagePrice = 0;
    }
    goodsObjs[row][3] = new Double(averagePrice);
    goodsObjs[row][4] = new Boolean(false);    //是否修改
    goodsObjs[row][5] = new Integer(quantity);        //取得购买数量
    goodsObjs[row][6] = new Double(amount);
    return goodsObjs;
  }
}