帶java的攤銷計劃

Question

我需要計算一個人每年支付貸款的利息金額，並顯示每年貸款餘額的下降。我瞭解如何在紙上獲取數字，但我無法弄清楚如何爲其編寫代碼，而其他論壇根本沒有幫助。

一個例子是什麼它應該看起來像爲：

Enter loan amount: 90000 
Enter loan duration in years: 15 
Enter interest rate as a percent: 6.75 


For a 15 year loan of $90000.00 at 6.75% interest 

Monthly payment = $ 796.42 
Total interest = $ 53355.33 

Yearly Balances 
Year Interest Loan Balance 
1  5965.23  86408.21 
2  5715.14  82566.33  
3  5447.64  78456.94  
4  5161.51  74061.43  
5  4855.46  69359.87  
6  4528.10  64330.94  
7  4177.95  58951.87  
8  3803.41  53198.26  
9  3402.80  47044.03  
10  2974.29  40461.31  
11  2515.95  33420.24  
12  2025.70  25888.91  
13  1501.31  17833.19  
14  940.40  9216.58  
15  340.45  -0.00 

我目前有：

import java.util.*; 
public class Loan 
{ 
    public static void main(String[] args) 
    { 
    Scanner keyboard = new Scanner(System.in); 
    int loanAmount, loanDurationYears, month; 
    double interestRate, monthlyPayment, totalInterest; 

    System.out.print("Enter loan amount:"); 
    loanAmount = keyboard.nextInt(); 

     System.out.print("Enter loan duration in years:"); 
    loanDurationYears = keyboard.nextInt(); 

     System.out.print("Enter interest rate as a percent:"); 
    interestRate = keyboard.nextDouble(); 
    keyboard.close(); 

    System.out.println("Loan amount: $" + loanAmount); 
    System.out.println("Loan duration: " + loanDurationYears + " years"); 
    System.out.println("Interest rate: " + interestRate + "%"); 

    monthlyPayment = payment(loanAmount, loanDurationYears, interestRate); 
    totalInterest = ((monthlyPayment * (loanDurationYears*12))-loanAmount); 
    printTotals(loanAmount, loanDurationYears, interestRate, monthlyPayment, totalInterest); 
    } 
    public static double payment(int loanAmount, int loanDurationYears, double interestRate) 
    { 
     int a = loanAmount; 
     int n = (loanDurationYears*12); 
     double i = ((interestRate*.01)/12); 
     double monthlyPayment = a*(Math.pow((1+i),n)*i)/((Math.pow((1+i),n))-1); 
     return monthlyPayment; 
    } 
    public static void printTotals(int loanAmount, int loanDurationYears, double interestRate, double monthlyPayment, double totalInterest) 
    { 
     System.out.println("For a " + loanDurationYears + " year loan of $" + loanAmount + " at " + interestRate + "% interest:"); 
     System.out.printf("Monthly payment = $"+ "%.2f", monthlyPayment); 
     System.out.println(); 
     System.out.printf("Total interest = $"+ "%.2f", totalInterest); 
     System.out.println(); 
    } 
} 

Answer 1

和雙精度浮點數不應該用於貨幣，因爲小數部分不會一直精確。

但是，既然你必須使用雙打，我建議你將小數點向右移一點，直到你得到所有你需要的精度。

例如。 100.26將不會在任何時間儲存在雙倍數字上，但100260.00將會被儲存。這樣，您就不會丟失重要的十進制數字「.26」的精度，並在精確舍入的末尾添加精確的額外數字「0」（如果需要，否則停在「26」處）。

因爲100.26絕對不能存儲在雙精度上（否則您將失去小數精度），您將讀取用戶輸入爲字符串或BigDecimal類型，然後將該值乘以1000再乘以1000 。如果你使用一個字符串，你會發現點，刪除它，並將其放置在2/3點右側，然後轉換爲雙倍。

由於您將乘以1000，您的雙倍最大值將會受到更多限制，但是如果您不打算使用大數字，則可能不是問題。

您將使用x * 1000正常進行所有操作，並且在打印之前，您會將雙精度數據傳遞給您的某個精確數據類型，格式爲刪除* 1000並打印。

對於這種風格，你不需要特別的雙重，例如可以使用很長的時間，但是你去了，你會得到雙打的確切值。