Java 使用方法进行文件I/O

在我的程序中，使用扫描仪获取用户输入的文件名。用户在控制台中输入.txt文件名，我也在控制台中获得了输出，但现在如果我想使用此方法执行此程序：

 public static double deviation(File inputFile)

我如何实施我的计划

public static void main(String[] args) throws FileNotFoundException {
        // TODO Auto-generated method stub
        double number = 0;
        double n = 0;

        double sum = 0;
        double sum1 = 0;
        int count = 0;
        double mean = 0;


            Scanner Scanscan = new Scanner(System.in);
            System.out.print("Enter the name of the file: ");
            String filename = Scanscan.nextLine();

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


            while(reader.hasNext()){
                number = reader.nextDouble();
                sum = sum + number;
                sum1 = sum1 + Math.pow(number,2);
                n++;
            }

            double n1 = Math.sqrt(n);
            double sum11 = Math.sqrt(sum1);
            mean = sum / n;

            double n12 = Math.pow(n,2) - n;
            double n22 = Math.pow(sum, 2);
            double x = ( n * sum1 - n22) / (n12);
            double deviation = (Math.sqrt(x));

            System.out.println( "The standard deviation of the values in this file is: " + deviation);

        }

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通过将必要的部分移动到新方法中

public static double deviation(File inputFile){
    double number = 0;
    double n = 0;
    double sum = 0;
    double sum1 = 0;
    int count = 0;
    double mean = 0;

    Scanner reader = new Scanner(inputFile);
    while(reader.hasNext()){
        number = reader.nextDouble();
        sum = sum + number;
        sum1 = sum1 + Math.pow(number,2);
        n++;
    }

    double n1 = Math.sqrt(n);
    double sum11 = Math.sqrt(sum1);
    mean = sum / n;

    double n12 = Math.pow(n,2) - n;
    double n22 = Math.pow(sum, 2);
    double x = ( n * sum1 - n22) / (n12);
    return Math.sqrt(x);
}
public static void main(String[] args) throws FileNotFoundException {
    Scanner Scanscan = new Scanner(System.in);
    System.out.print("Enter the name of the file: ");
    String filename = Scanscan.nextLine();
    File inputFile = new File(filename);
    double deviation = deviation(inputFile);
    System.out.println( "The standard deviation of the values in this file is: " + deviation);
}

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现在还不清楚你在问什么——你是说“我如何将代码重构成一个方法？”