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Question

对此错误进行了一些研究，而且大多数看似简单。我查看是否有一些拼写错误，我没有注意到任何。我试图用printf打印几行。当我去编译这段代码时，它给了我一个＆＃34;找不到符号错误＆＃34;。可能是这些方法需要在方法中定义变量吗？错误只在我的printSales方法中完成。这不是成品，所以我可能会缩短一两件。但这是我的代码，任何帮助将不胜感激。

import java.util.Scanner;

public class Sales
{

    public static void main( String[] args)
    {
    Scanner input = new Scanner (System.in);
    System.out.print("Please enter a product number.");
    double product1 = 0;
    double product2 = 0;
    double product3 = 0;
    double product4 = 0;
    double product5 = 0;
    double sale;

    int userInput = input.nextInt();
        while(userInput != 0)
        {   
           if(userInput >= 1 && userInput <= 5)
           {
            switch(userInput)
            {
                case 1:  System.out.println("");
                        product1 ++;
                        sale += 2.98;
                         break;

            System.out.print("How many were sold?");             
            userInput = input.nextInt();

                case 2:  System.out.println("");
                        product2 ++;
                        sale += 4.50;
                         break;

            System.out.print("How many were sold?");
            userInput = input.nextInt();

                case 3: System.out.println("");
                        product3 ++;
                        sale += 9.98;
                         break;

            System.out.print("How many were sold?");
            userInput = input.nextInt();

                case 4: System.out.println("");
                        product4 ++;
                        sale += 4.49;
                         break;

            System.out.print("How many were sold?");
            userInput = input.nextInt();

                case 5:System.out.println("");
                        product5 ++;
                        sale += 6.87;
                         break;
            System.out.print("How many were sold?");
            userInput = input.nextInt();

            }//end switch
            } //end if
        else if (userInput != 0)
            bSystem.out.println("ERROR: Incorrect Product Number, Please Try Again");
            System.out.print("");
            userInput = input.nextInt();
        }//end while 
    } //end main
    public void printSales()
    {
    System.out.println();
    System.out.printf("Product 1: $%.2f\n", product1);
    System.out.printf("Product 2: $%.2f\n", product2);
    System.out.printf("Product 3: $%.2f\n", product3);
    System.out.printf("Product 4: $%.2f\n", product4);
    System.out.printf("Product 5: $%.2f\n", product5);
    } //end printSales
} //end class

Answer 1

这是变量范围的问题。您不能在另一种方法中引用一种方法中的变量。尝试重新定义printSales：

public void printSales(int product1, int product2, int product3, int product4, int product5)
{
    System.out.println();
    System.out.printf("Product 1: $%.2f\n", product1);
    System.out.printf("Product 2: $%.2f\n", product2);
    System.out.printf("Product 3: $%.2f\n", product3);
    System.out.printf("Product 4: $%.2f\n", product4);
    System.out.printf("Product 5: $%.2f\n", product5);
} //end printSales

然后当然你必须改变你打电话给printSales的方式（我看到你现在没有打电话，但也许你将来会打电话）：

printSales(product1, product2, product3, product4, product5);

确保product1，product2等都在相同的“范围”中 - 您无法进入另一种方法，或者进入if {}或{}或while {}阻止引用变量。< / p>

Answer 2

四个问题......

1

sale might not be initialised ...

您将sale变量声明为...

double sale;

作为局部变量，它没有默认值，因此执行sale += 2.98之类的操作会产生未定义的结果。

简单地将变量初始化为默认/起始值...

double sale = 0d;

2

包bSystem不存在
bSystem.out.println（＆＃34;错误：产品编号不正确，请再试一次＆＃34;）;

错字，它应该是System.out.println;）

3

错误：找不到符号 System.out.printf（＆＃34;产品1：$％。2f \ n＆＃34;，product1）;

值product1，product2，product3，product4和product5在printSales中没有任何意义，因为它们只有＃{1}}已在main中声明为局部变量。

通常情况下，我建议制作这些实例变量，但由于您在static的{{1}}上下文中运行，因此无法正常工作。相反，修改main方法以获取参数...

printSales

4

您应该收到一些关于＆＃39;无法访问的语句public void printSales(double product1, double product2, double product3, double product4, double product5) { ... } break , this caused by the fact that you switch`语句的警告，但是会尝试执行代码...

out of the

相反，请尝试在case 1: System.out.println(""); product1++; sale += 2.98; break; System.out.print("How many were sold?"); userInput = input.nextInt(); ^--- These can't be executed, because of the break before it...语句之前移动代码....

break

您可能需要查看the Variables trail和Defining Methods了解更多详情

Answer 3

变量＆＃34; double product1 / 2/3 ......＆＃34;是本地变量，即它们的范围和生命周期在主方法中受到限制 - 您无法从printSales（）到达它们。

要解决问题并能够修改/调用变量，请将它们改为字段。也就是说，将它们放在类的上下文中，而不是方法。

public class Sales
{    
//variables moved into the context of the class, i.e. you can reach them from
//all methods of this class. Furhermore, they have to be static in order to be
//accessed from a static method.
private static double product1 = 0;
private static double product2 = 0;
private static double product3 = 0;
private static double product4 = 0;
private static double product5 = 0;
private static double sale;

public static void main( String[] args)
{
    Scanner input = new Scanner (System.in);
    System.out.print("Please enter a product number.");
    //rest of main method but without vairables
}

在printf行上找不到符号

3 个答案:

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3

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