ssd3: Exercise 1 Shopping Cart Application-优快云博客

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
}