求一个借款还贷计算器的JAVA程序

做一个计算器
输入贷款本金 贷款期（24-60个月） 月利率
就可以算出每月还款额

import javax.swing.JOptionPane;

public class Pay {
public static void main(String args[]){

String loanString = JOptionPane.showInputDialog("请输入贷款本金（ loanAmout）:such as 20000.00") ;

double loanAmount= Double.parseDouble(loanString);

String dateString = JOptionPane.showInputDialog("请输入贷款期（loanDate）:between 24-60");

int loanDate = Integer.parseInt(dateString);

String monthRateString = JOptionPane.showInputDialog("请输入月利率 (MonthRate):such as 0.00005");

double monthRate = Double.parseDouble(monthRateString);

double pay_Per_Month = (loanAmount+loanAmount * loanDate * monthRate)/loanDate;

JOptionPane.showMessageDialog(null, pay_Per_Month);
}
}