复利计算器没有给我正确的数据？

Question

我有一个复利计算器，但是当我运行代码并在它要求时输入以下数字时：

本金：10000 率：0.02 年：10

并选择已经设置好的“Annual”，这样如果我或用户输入该特定字符串，则选择变量将自动变为 1（或者如果我输入单词 Quarterly 或 Monthly，则其他值已经设置）。但是，我应该得到的价值是：12189.94 美元，而我得到的价值是：10200.0 我的代码哪里做错了？

import java.util.Scanner;
import java.lang.Math;
public class CompoundInterest {

public static void main (String [] args)
        { 
            Scanner cool = new Scanner (System.in);
double saving, rate;
int principal, years;
int choice;

System.out.println("Please enter you principal investment:");
/*Print statment prompts user to enter their principal investment*/
principal = cool.nextInt();

 System.out.println("Would you like to have a regular investment plan?");
/* Print out statement asks user if they would like to participate in a regular investment plan*/
String question =cool.next();

System.out.println("Please enter the number of years that you wish to invest for:");
/* Print statement prompts user to enter the number of years that they wish to invest for*/
years = cool.nextInt();

System.out.println("Please enter the return rate per year:");
/* Print statement prompts user to enter the return rate per year*/
rate = cool.nextDouble();

 System.out.println("What type of investment plan would you prefer (Annual, Quarterly, or Monthly)?");
String quest =cool.next();

 if ("Annual".equalsIgnoreCase(quest))
{ choice =1;

 }
 else if ("Quarterly".equalsIgnoreCase(quest)){
     choice = 4;
 }
 else if ("Monthly".equalsIgnoreCase(quest)){
     choice = 12;
 }
 else {
     choice = 0;
     System.out.println("Please choose a investment plan or speak to a financial advisor.");
 }

saving = principal*(1+(rate/choice))*Math.pow(choice,years);
System.out.println(saving);

Answer 1

感谢大家提供建议。看来我需要使用：

saving = principal * Math.pow(1+(double) (rate/ (choice)), choice * years);

为了让我的等式工作，因为我的等式似乎没有正确考虑我的整数值，因为保存被归类为双精度值。

Answer 2

您计算利息的公式不正确。应该是：

saving = principal*Math.pow(1+(rate/choice), choice*years);

在此处查看正确的公式：https://en.wikipedia.org/wiki/Compound_interest#Periodic_compounding