无法弄清楚为什么循环没有得到正确的总和

Question

我正在尝试制作一个抵押贷款计算器，但无论出于何种原因，本金和利息的总和是错误的。有没有可能是因为它是在 do-while 循环中添加的，所以它出错了？当我运行程序时，本金为 8233.68，利息为 11423.59。如果用计算器加起来的话，本金应该是8209.30，利息应该是11447.97

double termSelection = 0.0359;
double principal = 325000;
double effectiveMonthlyRate = 0.0029695338579054376;  
double monthlyPayment = 1638.1053796234314;
double monthlyInterest = (principal * effectiveMonthlyRate);
double monthlyPrincipal = (monthlyPayment - monthlyInterest);
double closingBalance = (principal - monthlyPrincipal);
 
int month = 1;
double totalPrincipal = 0;
double totalInterest = 0;
termSelection *= 100;

//monthly payment schedule header
System.out.println("");
System.out.printf("%nInterest Rate: %.2f%%", termSelection);
System.out.printf("%n%53s", "Monthly Payment Schedule");
termSelection /= 100;

//monhtly payment schedule body
System.out.printf("%n%5s%14s%15s%15s%15s%15s", "Month", "Open Bal", "Payment", "Princ", "Interest", "Closing Bal");

do{
    System.out.printf("%n%5s%14.2f%15.2f%15.2f%15.2f%15.2f", month, principal, monthlyPayment, monthlyPrincipal, monthlyInterest, closingBalance);
    
    month++;
    
    principal = closingBalance;
    
    monthlyInterest = principal * effectiveMonthlyRate; 
    
    monthlyPrincipal = monthlyPayment - monthlyInterest;
    
    closingBalance = principal - monthlyPrincipal;
    
    totalPrincipal = totalPrincipal + monthlyPrincipal;
    
    totalInterest = totalInterest + monthlyInterest;
    }
while (month <= 12); 

System.out.println("");
for (int count = 0; count <= 80; count++){
    System.out.print('=');
}

System.out.printf("%n%5s%44.2f%15.2f", "Ttls", totalPrincipal, totalInterest);

Answer 1

您在循环的第一次迭代中重新计算 monthlyInterest 和 monthlyPrincipal 的初始值，然后将它们添加到总计中。先将它们加到总数中，然后重新计算。

    do {
        System.out.printf("%n%5s%14.2f%15.2f%15.2f%15.2f%15.2f", month, principal, monthlyPayment, monthlyPrincipal, monthlyInterest, closingBalance);

        principal = closingBalance;
        totalPrincipal += monthlyPrincipal;
        totalInterest += monthlyInterest;

        monthlyInterest = principal * effectiveMonthlyRate;
        monthlyPrincipal = monthlyPayment - monthlyInterest;

        closingBalance = principal - monthlyPrincipal;

        month++;
    } while (month <= 12);

Answer 2

问题是你还没进入循环就开始计算了

double closingBalance = (principal - monthlyPrincipal);

应该是

double closingBalance = (principal);

输出

 Ttls                                     8209.30       11447.97

无法弄清楚为什么循环没有得到正确的总和

Cannot figure out why loop isn't getting the correct sum

java

loops

sum

do-while