ssd3: Exercise 1 Shopping Cart Application

该博客展示了如何创建一个简单的购物车应用,利用java.io和java.util.StringTokenizer处理用户输入,添加商品,显示商品列表及总价。文章通过示例代码讲解了StringTokenizer的用法和异常处理技巧。

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import  java.io.*;
import  java.util.*;

public class ShoppingCartApplication  {

 private static BufferedReader  stdIn =
  new  BufferedReader(new  InputStreamReader(System.in));
 private static PrintWriter  stdOut =
  new  PrintWriter(System.out, true);
 private static PrintWriter  stdErr =
  new  PrintWriter(System.err, true);

 private ShoppingCart cart;

 public static void main(String[]  args) throws IOException  {

  ShoppingCartApplication application = new  ShoppingCartApplication();

  application.run();
 }

 private void run() throws IOException  {

  cart = new  ShoppingCart();

  int  choice = getChoice();

  while (choice != 0)  {

   if (choice == 1)  {
    cart.addProduct(readProduct());
   } else if (choice == 2)  {
    stdOut.println(cart.toString());
   } else if (choice == 3)  {
    stdOut.println(cart.getTotalValue());
   }

   choice = getChoice();
  }
 }

 private int  getChoice() throws IOException  {

  do  {

   int input;

   try  {
    stdErr.println();
    stdErr.print("[0]  Quit/n"
                 + "[1]  Add Product/n"
                 + "[2]  Display Products/n"
                 + "[3]  Display Total/n"
                 + "choice>");
    stdErr.flush();

    input = Integer.parseInt(stdIn.readLine());

    if (0 <= input && 3 >= input)  {

     return  input;

    } else {
     stdErr.println("Invalid choice:  " + input);
    }
   } catch (NumberFormatException  nfe)  {
    stdErr.println(nfe);
   }
  }  while (true);
 }

 private Product readProduct() throws IOException {

  final String DELIM = "_";

  String name = "";
  int quantity = 0;
  double price = 0.0;


  /* PLACE YOUR CODE HERE */
  
  boolean flag=true;                                                             
  while(flag)  {                                                                         //进入输入的循环
  stdErr.print("product [name_qty_price]> ");                         //提示输入
  stdErr.flush();
  String readLine = stdIn.readLine();                                      //读取输入
  StringTokenizer st = new StringTokenizer(readLine, "_");
  
  if(st.countTokens() == 3)  {
    try  {
    name = st.nextToken();
    quantity = Integer.parseInt(st.nextToken());
    price = Double.parseDouble(st.nextToken());
    flag = false;                                                                         //如果输入正确,flag=false,退出循环
    }catch(NumberFormatException nfe)  {                              //类型错误
        stdErr.println("Invalid input");
        flag = true;                                                                     //进入新一轮循环,重新输入
     }finally  {
        if(quantity <= 0 || price <= 0)  {                                     //数据不符合
        stdErr.println("Invalid input");
        flag = true;                                                                     //进入新一轮循环,重新输入
       } 
     }
  }
  else  {                                                                                  //输入格式错误
    stdErr.println("Invalid input");
    flag = true;
  }
 }
 return new Product(name, quantity, price);                           //成功读取数据
 }

}

 

 

 

考察:

1.对java.util.StringTokenizer用法的掌握

2.对各类异常的处理

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