java弹出提示窗口的使用和包装类中的拆箱

import javax.swing.JOptionPane;
public class ComputeLoanUsingInputDialog {
  public static void main(String[] args) {
    // Enter yearly interest rate 通过弹出窗口获取用户的输入（注：获取的都为字符串类型）
    String annualInterestRateString = JOptionPane.showInputDialog(
      "Enter yearly interest rate, for example 8.25:");
    // Convert string to double 通过浮点数包装类中的方法把字符串转换为浮点数（注：只能转换纯数字不能包括字符）
    double annualInterestRate =
      Double.parseDouble(annualInterestRateString);
    // Obtain monthly interest rate
    double monthlyInterestRate = annualInterestRate / 1200;

    // Enter number of years 通过弹出窗口获取用户的输入（注：获取的都为字符串类型）
    String numberOfYearsString = JOptionPane.showInputDialog(
      "Enter number of years as an integer, \nfor example 5:");
    // Convert string to int 通过整数包装类中的方法把字符串转换为浮点数（注：只能转换纯数字不能包括字符）
    int numberOfYears = Integer.parseInt(numberOfYearsString);
    // Enter loan amount
    String loanString = JOptionPane.showInputDialog(
      "Enter loan amount, for example 120000.95:");
    // Convert string to double
    double loanAmount = Double.parseDouble(loanString);
    // Calculate payment
    double monthlyPayment = loanAmount * monthlyInterestRate / (1
      - 1 / Math.pow(1 + monthlyInterestRate, 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);
  }
}