import java.util.Date;

 import java.util.Random;

 import java.util.UUID;

 /**

  * @Name RandomStringUtil

  * @Descr 生成随机字符串

  * @author lnexin@aliyun.com

  * @date 2015年10月15日下午2:36:05

  */

 public class RandomStringUtil {

     /**

      * @param passLength

      *            : 要生成多少长度的字符串

      * @param type

      *            : 需要哪种类型

      * @return 根据传入的type来判定

      */

     // 可以根据自己需求来删减下面的代码，不要要的类型可以删掉

     // type=0：纯数字(0-9)

     // type=1：全小写字母(a-z)

     // type=2：全大写字母(A-Z)

     // type=3: 数字+小写字母

     // type=4: 数字+大写字母

     // type=5：大写字母+小写字母

     // type=6：数字+大写字母+小写字母

     // type=7：固定长度33位：根据UUID拿到的随机字符串，去掉了四个"-"(相当于长度33位的小写字母加数字)

     public static String getRandomCode(int passLength, int type) {

         StringBuffer buffer = null;

         StringBuffer sb = new StringBuffer();

         Random r = new Random();

         r.setSeed(new Date().getTime());

         switch (type) {

         case 0:

             buffer = new StringBuffer("0123456789");

             break;

         case 1:

             buffer = new StringBuffer("abcdefghijklmnopqrstuvwxyz");

             break;

         case 2:

             buffer = new StringBuffer("ABCDEFGHIJKLMNOPQRSTUVWXYZ");

             break;

         case 3:

             buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyz");

             break;

         case 4:

             buffer = new StringBuffer("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ");

             break;

         case 5:

             buffer = new StringBuffer("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");

             break;

         case 6:

             buffer = new StringBuffer("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789");

             sb.append(buffer.charAt(r.nextInt(buffer.length() - 10)));

             passLength -= 1;

             break;

         case 7:

             String s = UUID.randomUUID().toString();

             sb.append(s.substring(0, 8) + s.substring(9, 13) + s.substring(14, 18) + s.substring(19, 23) + s.substring(24));

         }

         if (type != 7) {

             int range = buffer.length();

             for (int i = 0; i < passLength; ++i) {

                 sb.append(buffer.charAt(r.nextInt(range)));

             }

         }

         return sb.toString();

     }

 }