Java:循环总计和错误:缺少返回语句

Question

我对 Java 还是个新手，我不知道如何让它保持运行总计。关于我应该查找什么的任何建议都会很棒。感谢您的时间。

import javax.swing.*;

public class OrderingProducts2

{

   public static double main(String[] args)

      {
         // Number of products 
         final int NUMBER_OF_PRODUCTS = 5;
         //all of the valid values 
         int[] validValues = {1, 2, 3, 4, 5};
         //prices that coralate with the values
         double[] prices = {2.98, 4.50, 9.98, 4.49, 6.87};
         //Starting total price of order
         double total = 0.00;
         //Sring for chosing a product to order

         String strProducts;

         int productOrdered;
         //Starting price of unnamed product
         double productPrice = 0.00;
         //boolean used to validate product
         boolean validProduct = false;
         //User input of product number
         strProducts = JOptionPane.showInputDialog(null,"Enter the product number you want to order or done");
         //product number being converted to an integer
         productOrdered = Integer.parseInt(strProducts);
         //string for getting the quanity 
         while(productOrdered > -1)
             {       
         String strQuanity;

         int productQuanity;
         //user input of quanity         
         strQuanity = JOptionPane.showInputDialog(null,"Enter the amount of product " + strProducts);
         //conversion of the quanity to an integer
         productQuanity = Integer.parseInt(strQuanity);
         //validation and totaling of the price of order    

         for(int x = 0; x < NUMBER_OF_PRODUCTS; ++x)

              {

               if(productOrdered == validValues[x])

                  {

                     validProduct = true;

                     productPrice = prices[x];

                     total = productPrice * productQuanity;

                   }                  

             }
             }
         //if there awas a valid out put this message will show
         if (validProduct)

         JOptionPane.showMessageDialog(null, "The price for product " + productOrdered + " is $" + productPrice + ". The price for your ordered item/items so far is $" + total);
         //if output was not valid this message will show
         else

         JOptionPane.showMessageDialog(null,"Sorry1 - invalid product entered");

Answer 1

为什么main的返回类型double？

应该是public static void main(String[] args)