编写程序计算贷款支付额

问题描述：程序要求用户输入月利率、还贷年数以及贷款金额，并要求显示月支付金额和总偿还金额。

给定的计算月支付额的公式如下：

月支付额= 贷款总额∗月利率1−1(1+月利率)(年数∗12)

则编写此程序的步骤为：

1) 使用图形用户界面（调用JOptionPane类）提示用户输入年利率、年数和贷款总额；

2) 利用年利率获取月利率；

3) 使用给定的公式计算月支付额；

4) 计算总支付额，总支付额=月支付额12年数；

5) 显示月支付额和总支付额。

以下为完整代码：

import javax.swing.JOptionPane;
public class ComputeLoan {

public static void main(String[] args) {
// TODO Auto-generated method stub
//Enter yearly interest rate
String yearlyRateString = JOptionPane.showInputDialog(
"Enter yearly interest rate,for example 8.25:");

//convert string to double
double yearlyRate = Double.parseDouble(yearlyRateString);

//obtain monthly interest rate
double monthlyRate = yearlyRate /1200;

//Enter number of years
String Years = JOptionPane.showInputDialog(
"Enter number of years as an integer,\nfor example 5:");

//convert string to int
int numberOfYears = Integer.parseInt(Years);

//Enter loan amount
String loanString = JOptionPane.showInputDialog(
"Enter loan number,for example 150000.95:");

//convert string to double
double loanAmount = Double.parseDouble(loanString);

//Calculate payment
double monthlyPayment = loanAmount * monthlyRate / (1 - 1 / Math.pow(1 + monthlyRate,numberOfYears * 12));

double totalPayment = monthlyPayment * numberOfYears * 12;

//Format to keep two digits after the decimal point
monthlyPayment = (int)(monthlyPayment * 100) / 100.0;
totalPayment = (int)(totalPayment * 100) / 100.0;

//Display results
String output = "The monthly payment is " + monthlyPayment +
"\nThe total payment is " + totalPayment;
JOptionPane.showMessageDialog(null, output);
}

}

运行结果如下所示：