课后小程序

 1 //信1605-3班  20163429  刘瑞欣
 2 package Yichang;
 3 import java.util.*;
 4 
 5 class AException extends Exception
 6 {
 7     String a;
 8     AException()  
 9     {
10         a="输入有误";   
11     }
12     public String toString()
13     {
14         return a;
15     }
16 }
17  
18 class Chengji 
19 { 
20     public static void main(String args[]) 
21     { 
22      while(1>0)
23        {
24          Scanner sc = new Scanner(System.in); 
25          System.out.println("请输入考试成绩（0~100）："); 
26         try 
27         { 
28             String s = sc.nextLine();     
29             getnum(s); 
30         } 
31         catch (AException e) 
32         { 
33             System.out.println(e.toString()); 
34         } 
35        }
36     } 
37 
38     private static void getnum(String s) throws AException 
39     { 
40         for (int i = s.length()-1; i >= 0;i--) 
41            {
42             int chr = s.charAt(i);
43           if (chr < 48 || chr > 57)
44           {
45 
46               throw new AException(); 
47 
48           }
49         }  
50         double num = Double.parseDouble(s);   
51         if (num < 0 || num> 100) 
52         { 
53             throw new AException(); 
54         } 
55         if (num>= 0 && num< 60)
56         { 
57             System.out.print("不及格
"); 
58         } 
59         else if (num >= 60 && num <= 70) 
60         { 
61             System.out.print("及格
"); 
62         } 
63         else if (num>= 70 && num<= 80) 
64         { 
65             System.out.print("中
"); 
66         }
67         else if (num >= 80 && num <= 90) 
68         { 
69             System.out.print("良
"); 
70         } 
71         else 
72         { 
73             System.out.print("优
"); 
74         } 
75     } 
76 }
直接输入回车就崩溃了。其他都不会崩溃。