只要用户插入双精度字，程序就会崩溃

Question

我已经编写了代码（包括Haversine部分），如果用户仅提供整数作为输入，则可以正常工作。问题是，当用户在扫描仪中输入双精度字符（甚至声明了双精度变量的地方）时，出现此错误：

线程“主”中的异常java.util.InputMismatchException

我的代码如下：

import java.util.Scanner;

public class TripPlanner {

public static final double PI = 3.14159;
public static final double r = 6367.51; 
public static void main(String[] args)  {
      greeting();
      travelTimeAndBudget();
      timeDifference();
      countryArea();
      howFar();
} 

public static void greeting()   {
      Scanner input = new Scanner(System.in);
      System.out.println("Welcome to Vacation Planner!");
      System.out.print("What is your name? ");
      String name = input.nextLine();
      System.out.print("Nice to meet you " + name + ", where are you travelling to? ");
      String place = input.nextLine();
      System.out.println("Great! " + place + " sounds like a great trip!");
} 

public static void travelTimeAndBudget()    {
      Scanner input = new Scanner(System.in);
      int hours = 24;     int minutes = hours*60;
      System.out.print("How many days are you going to spend travelling? ");
      int days = input.nextInt();
      System.out.print("How much money, in USD, are you planning to spend on your trip? ");
      double money = input.nextDouble();
      System.out.print("What is the three letter currency symbol for your travel destination? ");
      String currency = input.next();
      System.out.print("How many " + currency + " are there in 1 USD? ");
      double conversion = input.nextDouble();
      System.out.println("If you are travelling for " + days + " days that is the same as " + (days*hours) + " hours or " + (days*minutes) + " minutes");
      System.out.println("If you are going to spend $" + money + " USD that means per day you can spend up to $" + ((int)(100 * money / days) / 100.0) + "USD");
      System.out.println("Your total budget in " + currency + " is " + (conversion*money) + " which per day is " + ((int)(100 * conversion * money / days) / 100.0));
} 

public static void timeDifference() {
      Scanner input = new Scanner(System.in);
      System.out.print("What is the difference, in hours, between your home and your destination? ");
      int hourDifference = input.nextInt();
      System.out.println("That means that when it is midnight at home it will be " + hourDifference + ":00 in your travel destination and when it's noon at home it will be " + (hourDifference+12) + ":00");
} 

public static void countryArea()    {
      Scanner input = new Scanner(System.in);
      System.out.print("What is the square area of your destination country in km2? ");
      double area = input.nextDouble();
      System.out.println("In square miles that is " + ((int)(38.6102*area)/100.0));
}  

public static void howFar() {
      Scanner input = new Scanner(System.in);
      System.out.print("What are the latitude coordinates in degrees of your destination city? (positive for north, negative for south) ");
      double latDest = input.nextDouble();
      System.out.print("What are the longitude coordinates in degrees of your destination city? (positive for east, negative for west) ");
      double longDest = input.nextDouble();
      System.out.print("What are the latitude coordinates in degrees of your home city? (positive for north, negative for south) ");
      double latHome = input.nextDouble();     System.out.print("What are the longitude coordinates in degrees of your home city? (positive for east, negative for west) ");
      double longHome = input.nextDouble();
      latDest *= PI/180;
      longDest *= PI/180;
      latHome *= PI/180;
      longHome *= PI/180;
      double havLat = (1-Math.cos(latDest-latHome))/2;
      double havLong = (1-Math.cos(longDest-longHome))/2;
      double haversine = havLat + Math.cos(latHome) * Math.cos(latDest) * havLong;
      double distance = 2 * r * Math.asin(Math.sqrt(haversine));
      System.out.println("The distance between your home city and your destination is " + ((int)(distance*100)/100.0) + "km."); 
} 

Answer 1

这就是Scanner.nextInt（）的工作方式。看看这个，例如：https://examples.javacodegeeks.com/java-basics/exceptions/java-util-inputmismatchexception-how-to-solve-inputmismatchexception/

要处理双精度和整数输入，您可以使用例如Scanner.nextDouble（），然后将其转换为整数。