为什么我的代码不显示 presentValue？

Question

包裹现值； 导入 java.util.Scanner;

公共类 PresentValue {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
   double P; // present value
   double F; // future value
   double r; // annual interest rate
   double n; // number of years

   P = presentValue();

   F = futureValue();

   r = annualInterest();

   n = years();

   System.exit(0);
}
public static double presentValue()
{
    int input;
    Scanner keyboard = new Scanner(System.in);
      System.out.println("What is the presnt value of you savings account?");
       return keyboard.nextDouble();
}
public static double futureValue()
{
    int input;
    Scanner keyboard = new Scanner(System.in);
      System.out.println("How much do you want in your account in the future?");
      return keyboard.nextDouble();
}
public static double annualInterest()
{
    int input;
    Scanner keyboard = new Scanner(System.in);
    System.out.println("What is youe bank's interest rate?");
    return keyboard.nextDouble();
}
public static double years()
{
    int input;
    Scanner keyboard = new Scanner(System.in);
    System.out.println("How many  years will the money in the bank?");
    return keyboard.nextDouble();
}
public static double presentValue(double F, double r)
{
    return F/(1+(r * r));
}
public static void show(double presentValue)
{
    System.out.println(presentValue);
}

} 问题是写一个方法 presentValue 来执行这个计算。该方法应接受未来值、年利率和年数作为参数。它应该返回现值，即您今天需要存入的金额。在程序中演示该方法，让用户对公式中的项使用不同的值进行试验。

这里是公式 P = F/(1+r)^2

Answer 1

你必须使用Math.pow:

public static double presentValue(double future, double intrest, double years)
{
    return future / Math.pow(1.0 + intrest, years);
}

请注意，我添加了年数。您说的是两年，但我认为您确实希望有一个参数来指定年数，因为否则您不会向用户询问年数，对吗？