Java贷款表计算器

Question

我正在尝试编写一个贷款计算器。我在计算每月付款时遇到问题。我正在尝试打印出不同利率从低到高的每月还款额，增量为 0.25%。

我怀疑我的 while 循环有问题。有什么建议吗？

我一直很感谢你的帮助。我正在努力改进我的问题。

import apcslib.Format;
import chn.util.*;

public class loanTable {


    public static void main(String[] args) {
        //Declaring Variables
        double k;
        double n;
        double c;
        double p;
        double a;
        double low;
        double high;

        int time;

        //Getting User Input
        ConsoleIO console = new ConsoleIO();

        System.out.println("Amount of the loan: ");
        p = console.readDouble();
        System.out.println("Principal = $" + p);

        System.out.println("The length of loan in years: ");
        time = console.readInt();
        System.out.println("Time = " + time + " years");

        System.out.println("A low interest rate in %: ");
        low = console.readDouble() / 100;
        System.out.println("Low rate = " + low + "%");

        System.out.println("A high interest rate in %: ");
        high = console.readDouble() / 100;
        System.out.println("High rate = " + high + "%");

        //While Loop
        while (low <= high) {

            k = low / 1200.0;
            n = time * 12;
            c = Math.pow((1 + k), n);
            a = (p * k * c) / (c - 1);

            System.out.println("Annual interest rate: " + low * 100);
            System.out.println("Monthly Payment: " + Format.left(a, 2, 2));

            low += (0.25 / 100);
        }
    }

}

`

Answer 1

错误在于 k 的计算。应该是

 k = low /12;

这是正确的版本

public class loanTable {

 public static void main(String[] args) {
    //Declaring Variables
    double k;
    double n;
    double c;
    double p;
    double a;
    double low;
    double high;

    int time;

    System.out.println("Amount of the loan: ");
    p = 100000; 
    System.out.println("Principal = $" + p);

    System.out.println("The length of loan in years: ");
    time =30 ; 
    System.out.println("Time = " + time + " years");

    System.out.println("A low interest rate in %: ");
    low = 0.11; 
    System.out.println("Low rate = " + low + "%");

    System.out.println("A high interest rate in %: ");
    high = 0.1125; 
    System.out.println("High rate = " + high + "%");

    //While Loop
    while (low <= high) {
        //changed calculation of k
        k = low /12;
        n = time * 12;
        c = Math.pow((1 + k), n);
        a = (p * k * c) / (c - 1);

        System.out.println("Annual interest rate: " + (low * 100));
        System.out.println("Monthly Payment: " +a /* Format.left(a, 2, 2)*/);

        low += (0.25 / 100);
    }
  }
}

回答第二个问题(“我得到的输出直到年利率达到 11.75，但我需要增加到 12.00，我该怎么做？”):由于舍入误差，while 循环在 11.75 处停止。查看评论和一些克服它的替代方案:

public class LoanTable {

     public static void main(String[] args) {
        //Declaring Variables
        double k;
        double n;
        double c;
        double p;
        double a;
        double low;
        double high;

        int time;

        System.out.println("Amount of the loan: ");
        p = 100000;
        System.out.println("Principal = $" + p);

        System.out.println("The length of loan in years: ");
        time =30 ;
        System.out.println("Time = " + time + " years");

        System.out.println("A low interest rate in %: ");
        low = 0.11;
        System.out.println("Low rate = " + low + "%");

        System.out.println("A high interest rate in %: ");
        high = 0.12;
        System.out.println("High rate = " + high + "%");

        System.out.println("---------------- Not working well  ------------------");
        //While Loop
        while (low <= high) {
            /*
             * changed calculation of k
             */
            k = low /12;
            n = time * 12;
            c = Math.pow((1 + k), n);
            a = (p * k * c) / (c - 1);

            System.out.println("Annual interest rate: " + (low * 100));
            System.out.println("Monthly Payment: " +a /* Format.left(a, 2, 2)*/);

            low += (0.25 / 100);

            /*
             * at the 4th loop low = 0.12000000000000001
             * so low > high and while block is terminated.
             */
             System.out.println("low = "+ low);

         }

        System.out.println("---------------- Alternative 1  ------------------");
        //While Loop
        low = 0.11;
        high = 0.12;
        int counter = 0;
        double interest = low;

        while (  interest <=  high   ) {

            /*
             * changed calculation of k
             */
            k = interest /12;
            n = time * 12;
            c = Math.pow((1 + k), n);
            a = (p * k * c) / (c - 1);

            System.out.println("Annual interest rate: " + (interest * 100));
            System.out.println("Monthly Payment: " +a /* Format.left(a, 2, 2)*/);

            counter++;
            /*
             * recalculate interest from low, to avoid accumulating 
             * rounding error 
             */
            interest = low + ((0.25/100)* counter);
         }

        System.out.println("---------------- Alternative 2  ------------------");
        //While Loop
        low = 0.11;
        high = 0.12;

        /*
         * cast float to reduce the accuracy. A better alternative would be
         * to declare low and high as float
         */
        while (  (float)low <=  (float)high   ) {
            /*
             * changed calculation of k
             */
            k = low /12;
            n = time * 12;
            c = Math.pow((1 + k), n);
            a = (p * k * c) / (c - 1);

            System.out.println("Annual interest rate: " + (low * 100));
            System.out.println("Monthly Payment: " +a /* Format.left(a, 2, 2)*/);

            low += (0.25 / 100);

         }

        System.out.println("---------------- Alternative 3  ------------------");

        //While Loop
        /*
         * work with integer
         */
        int lowInterest  = 1100;
        int highInterest = 1200;

        while (  lowInterest <=  highInterest  ) {
            /*
             * changed calculation of k
             */
            k = (float)lowInterest /(12*10000);
            n = time * 12;
            c = Math.pow((1 + k), n);
            a = (p * k * c) / (c - 1);

            System.out.println("Annual interest rate: " + ((float)lowInterest /100));
            System.out.println("Monthly Payment: " +a /* Format.left(a, 2, 2)*/);

            lowInterest += 25;

         }

      }
    }