Java空指针异常NullPointerException 

 1 package varycode;
 2 
 3 import java.util.ArrayList;
 4 import java.util.Random;
 5 
 6 public class VaryCodeDemo {
 7 
 8     public static void main(String[] args) {
 9         // TODO 自动生成的方法存根
10         VaryCode test1=new VaryCode(null);
11         Random r2=new Random(2);
12         int choice ;
13         char c[] = {'a','b','c','d','e','f'};
14         
15         
16         for(int i=0;i<6;i++) {
17             choice = r2.nextInt(1)*7;
18         switch(choice) {
19         case 1:
20             c[0]=test1.downC();
21             break;
22         case 2:
23             c[1]=test1.downC();
24             break;
25         case 3:
26             c[2]=test1.downC();
27             break;
28         case 4:
29             c[3]=(char) test1.num();
30             break;
31         case 5:
32             c[4]=(char) test1.num();
33             break;
34         case 6:
35             c[5]=test1.downC();
36             break;
37             }
38         }
39         for(int i=0;i<6;i++) {
40                System.out.print(c[i]);
41             }
42         }
43     }
 1 package varycode;
 2 
 3 import java.util.ArrayList;
 4 import java.util.Random;
 5 
 6 public class VaryCodeDemo {
 7 
 8     public static void main(String[] args) {
 9         // TODO 自动生成的方法存根
10         VaryCode test1=new VaryCode(null);
11         Random r2=new Random(2);
12         int choice ;
13         char c[] = {'a','b','c','d','e','f'};
14         
15         
16         for(int i=0;i<6;i++) {
17             choice = r2.nextInt(1)*7;
18         switch(choice) {
19         case 1:
20             c[0]=test1.downC();
21             break;
22         case 2:
23             c[1]=test1.downC();
24             break;
25         case 3:
26             c[2]=test1.downC();
27             break;
28         case 4:
29             c[3]=(char) test1.num();
30             break;
31         case 5:
32             c[4]=(char) test1.num();
33             break;
34         case 6:
35             c[5]=test1.downC();
36             break;
37             }
38         }
39         for(int i=0;i<6;i++) {
40                System.out.print(c[i]);
41             }
42         }
43     }

 


遇到的问题：

无法赋值

空指针异常

posted @ 2020-10-05 23:05  靠谱杨  阅读(128)  评论(0)    收藏  举报