Java扫描程序错误[重复]

Question

import java.util.Scanner;

public class ComputeLoan {
    public static void main(String[] args) {
    // Create a Scanner
    Scanner input = new Scanner(System.in);

    //Enter annual interest rate in percentage e.g., 7.25%
    System.out.print("Enter annual interest rate in, e.g., 7.25%: ");
    double annualInterestRate = input.nextDouble();

    // Obtain monthly interest rate
    double monthlyInterestRate = annualInterestRate / 1200;

    //Enter number of years
    System.out.print(
      "Enter number of years as an integer, e.g., 5: ");
    int numberOfYears = input.nextInt();

    // Enter loan amount
    double loanAmount = input.nextDouble();

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

    double totalPayment = monthlyPayment * numberOfYears * 12;


    // Display results
    System.out.println("The monthly payment is $" + (int) (monthlyPayment * 100) / 100.0);
    System.out.println("The total payment is $" + (int) (totalPayment * 100) / 100.0);

    }
}

控制台：

Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:864)
    at java.util.Scanner.next(Scanner.java:1485)
    at java.util.Scanner.nextDouble(Scanner.java:2413)
    at ComputeLoan.main(ComputeLoan.java:10)

Answer 1

这里：

 System.out.print("Enter annual interest rate in, e.g., 7.25%: ");
 double annualInterestRate = input.nextDouble();

在控制台输入值时，输入值为7.25，而不是7.25%

一个很好的做法是：在命令行上接受来自用户的值时，总是以string的形式接受它们，即input.nextline()，然后使用parse方法将其解析为适当的类型。如果在解析时发生异常，这意味着用户没有正确输入，请通知用户并继续。

while(true) {
      try {
            System.out.print("Enter annual interest rate in, e.g., 7.25%: ");
            double annualInterestRate = Double.parseDouble(input.nextLine());
            break;
          } 
     catch(NumberFormatException nfe) {
                System.out.print("Wrong input,enter again");
            }
       }