实例变量重置

Question

在方法 checker() 和 runFirst 之间，变量“running”和“productChoice”被重置，我不知道为什么。我尝试过如何声明 RetailSalesProgram，但似乎没有任何效果。我只需要知道如何使变量不重置。

import javax.swing.JOptionPane;
public class RetailSalesProgram
{
private String customerName = "Default";
private int customerChoice;
private boolean running;
private double productChoice, a, b, c ,d ,e, total;
   // sets values
   public RetailSalesProgram()
   {
      running = true;
      a= 2.98;
      b= 4.50;
      c= 9.98;
      d= 3.15;
      e= 2.29;
   }
   / takes the methods and puts them into main
   public void runFirst()
   {
      RetailSalesProgram rsp = new RetailSalesProgram();
      rsp.greet();
      do
      {
      rsp.shop();
      rsp.checker();
      rsp.totaling();
      System.out.println(running);
      System.out.println(total);
      }
      while (running == true);


   }

   //the initial greeting before they shop
   private void greet()
   {
      customerName = JOptionPane.showInputDialog(null, " Welcome to my store!\n Please enter your name");
      JOptionPane.showMessageDialog(null, "Hello " + customerName + "!");
   }
   //this is the menu for the shop
   private void shop()
   {
      customerChoice = Integer.parseInt(JOptionPane.showInputDialog(null, " 1. Can of beans  $2.98\n2. Calculator  $4.50\n3. Yoga mat  $9.98\n4. Bottle of Gatorade  $$3.15\n5. Birthday card  $2.29\n6. Exit program"));
      while (customerChoice < 1 || customerChoice > 6)
      {
         JOptionPane.showMessageDialog(null, "That was not a valid entry");
         customerChoice = Integer.parseInt(JOptionPane.showInputDialog(null, " 1. Can of beans  $2.98\n2. Calculator  $4.50\n3. Yoga mat  $9.98\n4. Bottle of Gatorade  $$3.15\n5. Birthday card  $2.29\n6. Exit program"));
      }
      System.out.println(customerChoice);
   }
   // This is where im having problems. It is suppose to change the instance variables.
   private void checker()
   {
   switch (customerChoice)
      {
      case 1: 
               productChoice = a;
               break;
      case 2: 
               productChoice = b;
               break;
      case 3: 
               productChoice = c;
               break;
      case 4: 
               productChoice = d;
               break;
      case 5: 
               productChoice = e;
               break;
      case 6: 
               running = false;
               break;
      } 
                     System.out.println(total);
                     System.out.println(running);
   }
   // This just takes a total of the product.
   private void totaling()
   {
      productChoice += total;
   }


//////////////////////////////////////////////////////////////////////////
// will run everything for runFirst()   
   public static void main(String[]args)
   {
   RetailSalesProgram rsp = new RetailSalesProgram();
   rsp.runFirst();
   }
}

Answer 1

您有两个 rsp 变量。一个是字段，一个是局部变量。

private RetailSalesProgram rsp; // one variable
   // sets values
   public RetailSalesProgram()
   {
      RetailSalesProgram rsp = new RetailSalesProgram(); // unrelated variable.

您很可能根本不需要此字段，因为您已经有一个 RetailSalesProgram