在 Java 中出现 "cannot find symbol" 错误

Question

我正在编写一些代码来从文本板读取静态股票编号。我运行看看出了什么问题，我似乎无法修复这个找不到符号的错误。

import java.io.*;
import java.util.*;

public class StockMarket
{
    public static void main(String[] args) throws IOException
    {

        Scanner keyboard = new Scanner(System.in);

        System.out.println("Enter the filename: ");
        String filename = keyboard.nextLine();

        File file = new File(filename);
        Scanner inputFile = new Scanner(file);

        while (inputFile.hasNext())
        {
            checkValidity();
        }

        inputFile.close();

    }

    public static boolean checkValidity()
    {

    String line = inputFile.nextLine();
    double numberOfShares = inputFile.nextDouble();
    double buyPricePerShare = inputFile.nextDouble();
    double buyComissionRate = inputFile.nextDouble();
    double sellPricePerShare = inputFile.nextDouble();
    double sellComissionRate = inputFile.nextDouble();

    }

}

Answer 1

您的方法checkValidity 行不通。您尝试访问方法中未知的变量 inputFile。您必须将 is 作为参数传递。

public static boolean checkValidity(Scanner inputFile)

{

String line = inputFile.nextLine();
double numberOfShares = inputFile.nextDouble();
double buyPricePerShare = inputFile.nextDouble();
double buyComissionRate = inputFile.nextDouble();
double sellPricePerShare = inputFile.nextDouble();
double sellComissionRate = inputFile.nextDouble();

}

Answer 2

您的 checkValidity() 方法几乎没有问题，如下所述：

(1) 您的 Scanner 对象作用域仅存在于 main 方法 中，因此将该对象传递给 checkValidity 方法

(2) 验证 checkValidity 方法中的输入

(3) 您的 checkValidity 方法具有 return 类型的 boolean，因此您需要 return 一个 boolean来自它的值 即，如果验证成功，return true 或者如果验证失败，return false

您参考以下带有内联注释的代码：

public static boolean checkValidity(Scanner inputFile) {
        String line = inputFile.nextLine();
        double numberOfShares = inputFile.nextDouble();
        double buyPricePerShare = inputFile.nextDouble();
        double buyComissionRate = inputFile.nextDouble();
        double sellPricePerShare = inputFile.nextDouble();
        double sellComissionRate = inputFile.nextDouble();
        boolean validationSuccess = false;
        //validate your inputs
        // If validations are successful  then set validationSuccess = true;
        return validationSuccess;//return boolean
    }

此外，从 main() 传递 scanner 对象，如下所示：

while (inputFile.hasNext()) {
     checkValidity(inputFile);//pass scanner object
}

在 Java 中出现 "cannot find symbol" 错误

Getting "cannot find symbol" error in Java

java

java.util.scanner

stock

cannot-find-symbol