1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
package  randomdata;
import  java.util.Random;
public  class  RandomCharData {
     //可以将字符转换赋值给int类型，查看其ASCII码
     public  static  void  main(String[] args) {
         //随机生成纯数字
         for ( int  i= 0 ;i< 15 ;i++)
             createData( 20 );
         System.out.println( "---------------" );
                           
         //生成数字字母
         for ( int  i= 0 ;i< 15 ;i++)
         createRandomCharData( 20 );
     }
     //根据指定长度生成字母和数字的随机数
     //0~9的ASCII为48~57
     //A~Z的ASCII为65~90
     //a~z的ASCII为97~122
     public  static  void  createRandomCharData( int  length)
     {
         StringBuilder sb= new  StringBuilder();
         Random rand= new  Random(); //随机用以下三个随机生成器
         Random randdata= new  Random();
         int  data= 0 ;
         for ( int  i= 0 ;i<length;i++)
         {
             int  index=rand.nextInt( 3 );
             //目的是随机选择生成数字，大小写字母
             switch (index)
             {
             case  0 :
                  data=randdata.nextInt( 10 ); //仅仅会生成0~9
                  sb.append(data);
                 break ;
             case  1 :
                 data=randdata.nextInt( 26 )+ 65 ; //保证只会产生65~90之间的整数
                 sb.append(( char )data);
                 break ;
             case  2 :
                 data=randdata.nextInt( 26 )+ 97 ; //保证只会产生97~122之间的整数
                 sb.append(( char )data);
                 break ;
             }
         }
         String result=sb.toString();
         System.out.println(result);
     }
                       
     //根据指定长度生成纯数字的随机数
     public  static  void  createData( int  length) {
         StringBuilder sb= new  StringBuilder();
         Random rand= new  Random();
         for ( int  i= 0 ;i<length;i++)
         {
             sb.append(rand.nextInt( 10 ));
         }
         String data=sb.toString();
         System.out.println(length+ " random data: " +data);
     }
}

产生结果如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
97862483216351602095
70514049428709111734
58909883924816310266
57687118857245129003
61026032192487969045
24071314312917474726
33994529915727126720
96782018153746273742
63798758707067214215
07076213273633627868
48227106476502535792
59944228129822555128
20025042941676211212
70116211781380045731
88967160116193801569
---------------
0Qa0cZYe6YyMf4zrLEzEJqK6f
MwwDl6Kan92RseOPWJuf6WpnF
0H1249B0Y7qoGmbj0ZWeCliId
PIsRRAS99XIbPwBqCdV7BUt7e
X6R5cotl638K83c4fowNv0S3j
03p7YzBA0q2OlB70pL4MTQf5P
7x5Yd57SOYGoTS9ABi8RA2F5y
1XVK9wrhrFxINd4gpi4Ip05Hg
r53YoB2aBgeP2i4061A2CMNK2
X1R3VWi7423VSs0j0u6R7uMy7
uCQ19SGe4U19V9U4XVqB5QDmc
2OaJ1O3JC52617kMTH2yK9yyJ
kM85MalnsR8T299yR8B0bP5DH
rAApB65VXpj4qxp0gEj4Oh34I
3k88S216XWbK83XaCTnvin02f