如何调用方法到主方法（程序运行但不打印问题）（作业）

响应之前的程序，只需放置 new Balance();其中 public static void main 是不起作用的，如果没有它，程序会运行，但nerner会打印出用户问题！

import java.io.*;

public class cInterest {

    public static void main(String[] args)   throws IOException
    {
       //new balance ; 
    }
    public static  double balance(double principal, double rate, double years) throws IOException{

        double amount = 0;

        String input;
        BufferedReader myInput = new BufferedReader (new InputStreamReader (System.in));

        System.out.print("How much would you like to take out? ");
        input = myInput.readLine ();
        principal = Double.parseDouble (input);        

        System.out.print("Enter the interest rate: ");
        input = myInput.readLine ();
        rate = Double.parseDouble (input);

        for (int i = 1; i < years; i++) {
            amount = principal * rate * years;
            amount += principal;
        }
        return amount; //- principal;
    }
}

balance是一个方法，而不是一个类，所以你不能使用new关键词。你想要call相反，方法如下：

public static void main(String[] args)   throws IOException
{
    double balance = balance(0.0, 0.0, 1.0); // Awkward hard-coded variables! Ew!
    System.out.println(balance);
}

但是，当用户要覆盖这些变量时，为什么要将它们传递给方法呢？你的balance方法应该只负责计算余额，而不是收集用户输入。您可以在main method:

public static void main(String[] args)   throws IOException
{
    // Gather user input.
    String input;
    BufferedReader myInput = new BufferedReader (new InputStreamReader (System.in));

    System.out.print("How much would you like to take out? ");
    input = myInput.readLine ();
    double principal = Double.parseDouble (input);        

    System.out.print("Enter the interest rate: ");
    input = myInput.readLine ();
    double rate = Double.parseDouble (input);

    System.out.print("Enter the number of years: ");
    input = myInput.readLine ();
    double years = Double.parseDouble (input);

    // Now do the calculations...
    double balance = balance(principal, rate, years); // Much clearer!
    System.out.println(balance);
}

public static double balance(double principal, double rate, double years) {
    // Calculate the end balance based on the parameters, and return it.
}

更好是将用户输入的收集放入其自己的专用方法中，但我已经远远偏离主题了。