需要协助显示来自不同私人课程的价值

Question

好的，首先我对java非常非常新。对于这个项目，我需要设计一个程序，它接受一个产品编号，一个销售的amoutn，计算总数，然后显示它。但是，当我选择选项2时，我需要显示，这是一个单独的私人课程，说实话我甚至不知道从哪里开始。任何帮助将不胜感激。

import java.util.Scanner;

public class Attempt1
{
//method to pause until a key is pressed
public static void pause() 
{ 
    try 
    { 
        System.out.print("Press <Enter> to continue..."); 
        System.in.read(); 
    } 
    catch (Exception e)
    {
        System.err.printf("Error %s%c\n",e.getMessage(),7);
    }
}//end pause

public static void main(String[] args)
{
    //variables to capture keyboard input
    Scanner keyBd = new Scanner( System.in );
    char selection;
    //int selection;

    do{//display menu
        System.out.println("\n--------------");
        System.out.println("Retail Sales\n");
        System.out.println("1. Enter Products Sold");
        System.out.println("2. Display Total Retail Sales");
        System.out.println("3. Exit\n");
        System.out.print  ("Selection: ");

        //get menu selection
        selection = keyBd.next().charAt(0);
        //selection = keyBd.nextInt();

        //process menu selection
        switch (selection){
            case '1':
                enterProducts();
                break;
            case '2':
                displaySales();
                break;
            case '3':               
                //recognize as valid selection but do nothing
                break;
            default :
                //System.out.printf("%c\n",7);
                System.out.println("Invalid Selection");
        }//end switch

    }while( selection != '3');

}//end main()

private static void enterProducts()
{
    Scanner inp = new Scanner(System.in);

    int product,quantity;
    double total = 0.00;

    System.out.print("Enter product #(1-5)(0 to stop): ");
    product=inp.nextInt();

    while(product !=0)
        {
        System.out.print("Enter quantity: ");
        quantity=inp.nextInt();
    switch( product ){
    case 1:total+=quantity*2.98;
    break;
    case 2:total+=quantity*4.50;
    break;
    case 3:total+=quantity*3.98;
    break;
    case 4:total+=quantity*4.49;
    break;
    case 5:total+=quantity*6.87;
    break;
    default:System.out.println("Invalid Product Number");
    System.out.println("Product Number Does not Exist");

    if(product<0 && product>=6)
      {
    System.out.print("Enter product #(1-5)(0 to stop): ");
    product=inp.nextInt();
    System.out.print("Enter quantity: ");
    quantity=inp.nextInt();
      }
    break;
    }
    System.out.print("Enter product #(1-5)(0 to stop): ");
    product=inp.nextInt(); 
    }

    pause();    
    }
private static void displaySales()
{
    System.out.println( "The total retail value was: " + total );
    pause();    
}

} //结束MenuDemo

Answer 1

我认为您的意思是private 方法。你可以像这样传递总数：

private static void displaySales(double total) {
...

total在enterProducts中定义，但未在显示循环的main方法中定义，因此您可以返回此内容：

double enterProducts() {
   ...
   return total;
}

以便您可以将其传递给displaySales。

Answer 2

以下是改进代码的算法：

1. 在您的主要文字开头添加变量total并将其初始化为0：double total=0;
2. 将enterProducts方法的返回类型更改为double private static double enterProducts()，并在调用total之后从此方法返回本地变量pause：{{1 }}
3. 如果输入return total;，则将1的返回值添加到当前值enterProducts（它是您主要内部的total）：{{ 1}}
4. 向方法total添加双重参数：total += enterProducts();并在displaySales到private static void displaySales(double total)
的主要情况下更改对其的调用

Answer 3

代码的问题在于您正在尝试访问静态enterSroducts（）方法中静态displaySales（）方法中声明的局部变量。

以下代码解决了“问题”。

话虽如此，我建议您通过一些Java教程来理解代码现在的工作原理......看看Variable Scope。

public class Attempt1
{
//use a static variable to store the total  
static double total = 0.00;

//method to pause until a key is pressed
public static void pause() 
{ 
    try 
    { 
        System.out.print("Press <Enter> to continue..."); 
        System.in.read(); 
    } 
    catch (Exception e)
    {
        System.err.printf("Error %s%c\n",e.getMessage(),7);
    }
}//end pause

public static void main(String[] args)
{
    //variables to capture keyboard input
    Scanner keyBd = new Scanner( System.in );
    char selection;
    //int selection;

    do{//display menu
        System.out.println("\n--------------");
        System.out.println("Retail Sales\n");
        System.out.println("1. Enter Products Sold");
        System.out.println("2. Display Total Retail Sales");
        System.out.println("3. Exit\n");
        System.out.print  ("Selection: ");

        //get menu selection
        selection = keyBd.next().charAt(0);
        //selection = keyBd.nextInt();

        //process menu selection
        switch (selection){
            case '1':
                enterProducts();
                break;
            case '2':
                displaySales();
                break;
            case '3':               
                //recognize as valid selection but do nothing
                break;
            default :
                //System.out.printf("%c\n",7);
                System.out.println("Invalid Selection");
        }//end switch

    }while( selection != '3');

}//end main()

private static void enterProducts()
{
    Scanner inp = new Scanner(System.in);

    int product,quantity;

    System.out.print("Enter product #(1-5)(0 to stop): ");
    product=inp.nextInt();

    while(product !=0)
        {
        System.out.print("Enter quantity: ");
        quantity=inp.nextInt();
    switch( product ){
    case 1:total+=quantity*2.98;
    break;
    case 2:total+=quantity*4.50;
    break;
    case 3:total+=quantity*3.98;
    break;
    case 4:total+=quantity*4.49;
    break;
    case 5:total+=quantity*6.87;
    break;
    default:System.out.println("Invalid Product Number");
    System.out.println("Product Number Does not Exist");

    if(product<0 && product>=6)
      {
    System.out.print("Enter product #(1-5)(0 to stop): ");
    product=inp.nextInt();
    System.out.print("Enter quantity: ");
    quantity=inp.nextInt();
      }
    break;
    }
    System.out.print("Enter product #(1-5)(0 to stop): ");
    product=inp.nextInt(); 
    }

    pause();    
    }
private static void displaySales()
{
    System.out.println( "The total retail value was: " + total );
    pause();    
}
}//end MenuDemo