java - 在无限循环中抛出异常。找不到我的出路。

Question

这个问题已经有答案了:

How to handle infinite loop caused by invalid input (InputMismatchException) using Scanner (5 个回答)

已关闭 5 年前。

当抛出 InputMismatchException 时，我进入了一个无限循环，我一生都无法弄清楚为什么。基本上，该程序的主要目标是针对用户输入的负数引发异常，并确保用户实际输入一个整数(而不是像“r45”这样的东西)。任何帮助将不胜感激。谢谢。

  import java.util.*;

  public class conversion{
  static Scanner in = new Scanner (System.in);
  static final double centimeters_per_inch = 2.54;
  static final int inches_per_foot = 12;

  public static void main (String [] args){
  int feet;
  int inches;
  int totalInches;
  double centimeters;
  boolean done = false;
  do{
    try
       {
       System.out.print("Enter feet: ");
       System.out.flush();
       feet = in.nextInt();
       System.out.println();
       System.out.print("Enter inches: ");
       System.out.flush();
       inches = in.nextInt();

       if (feet < 0 || inches < 0)
         throw new NonNegative();

       System.out.println();

       done = true;
       System.out.println("The numbers you entered are " + feet +" feet and " + inches+ " inches");
       totalInches = inches_per_foot * feet + inches;
       System.out.println();
       System.out.println("The total number of inches = " + totalInches);
       centimeters = totalInches * centimeters_per_inch;
       System.out.println("The number of centimeteres = " + centimeters); 
     }

     catch (NonNegative a){
       System.out.println(a.toString());   
     }
     catch(InputMismatchException e) {
       System.out.println("This is not a number");
     }
   }while(!done);
 }

}

Answer 1

当发生 InputMismatchException 时，来自 Scanner 的无效输入将通过 while 循环发回，并重复该过程无限。。调用 nextLine 以使用来自 Scanner 的非数字输入。这将防止未使用的数据被发送回循环

System.out.println("This is not a number " + in.nextLine());