shoppingcartapplication.java

ssd1 exercise 1的题目和答案

import  java.io.*;
import  java.util.*;
/**
 * This class represents a sequence of choices
 * and get the choice to do certain work of the Shopping Cart.
 *
 * @author  Libo Du 
 * @version  1.0.0
 */
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;
    /**
	 * Main method for class <code>ShoppingCartApplication</code>.
	 *
	 * @param args  not used.
	 */
	public static void main(String[]  args) throws IOException  {

		ShoppingCartApplication application = new  ShoppingCartApplication();

		application.run();
	}
    /**
	 * Invoke the <code>getChoice()</code> method and deal with the choice.
	 */
	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();
		}
	}
    /**
	 * Display the menu and get the choice.
	 *
	 * @return  The number of the choice.
	 */
	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);
	}
    /**
	 * Obitain the input of the <code>Product</code>,and use the input 
	 *data as parameters to generate the object of <code>Product</code>.
	 *
	 * @return object of the <code>Product</code>.          
	 */
	private Product readProduct() throws IOException {

		String name = "";
		int quantity = 0;
		double price = 0.0;
outer:while(true){
			stdOut.print("product [name_qty_price]> ");
			stdOut.flush();
			try{
		StringTokenizer  tokenizer =
            new  StringTokenizer(stdIn.readLine(),"_");
		if (tokenizer.countTokens() != 3) {
            stdErr.println("Invalid input");
            continue outer;
        } 
        else {
            name = tokenizer.nextToken();
            quantity = Integer.parseInt(tokenizer.nextToken());
            price = Double.parseDouble(tokenizer.nextToken());
        }
		if (quantity<=0||price<0.0D){
			stdErr.println("Invalid input");
			continue outer;}
			}
		catch (NumberFormatException  nfe)  {
		
            stdErr.println(nfe); 
            continue outer;
		}
		return new Product(name, quantity, price);
		}
	}
}