Java---计算机贷款支付额计算(用对话框实现)

本例演示如何编写程序来计算贷款支付问题。

下面是编写程序的步骤：

1.提示用户输入年利率、年数和贷款总额

2.利用年利率算出月利率

3.通过前面的公式计算月支付额。

4.计算总支付额，它是月支付额乘以12再乘以年数。

5.在消息对话框中显示月支付额和总支付额。

package cn.hncu.Chapter2;

import javax.swing.JOptionPane;

/**
* @author hncu_chx
*
* Mylove amin
*
*/
public class ComputeLoan {
public static void main(String[] args) {
//Enter yearly interest rate开始的年利率
String annualInterestRateString = JOptionPane.showInputDialog("Enter yearly " +
"interest rate,for example 8.25:");

//Convert转换… string to double
double annualInterestRate =
Double.parseDouble(annualInterestRateString);

//Obtain获得 monthly每月的 interest rate利息率
double monthlyInterestRate = annualInterestRate/1200;

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

//Convert转换 string to int
int numberOfYears = Integer.parseInt(numberOfYearsString);

//Enter开始 loan借款 amount总额
String loanString = JOptionPane.showInputDialog("Enter loan amount," +
"for example 120000.95:");

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

//Calculate 计算 payment付款，支付；报酬
double monthlyPayment = loanAmount * monthlyInterestRate/(1-1/Math.pow(1+monthlyInterestRate,
numberOfYears*12));
double totalPayment = monthlyPayment*numberOfYears*12;

//Format格式 to keep tow digits位数 数字 after the decimal小数 point点
//格式保留小数点后两位数
monthlyPayment = (int )(monthlyPayment *100)/100.0;
totalPayment = (int)(totalPayment *100)/100.0;

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

}

}

注意：如果在输入对话框中点击取消，无字符串返回，系统会出现运行时错误。