JAVA 随机字符串

<pre name="code" class="java">public class StringUtils{
      private static Random randGen = new Random();
      private static char[] letters =("0123456789abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
      //获取指定长度的随机字符串
      public static String randomString(int len){
           if(len<1){
              return null;
           }
           
           char[] buf= new char[len];
           for(int i=0;i<len;i++){
              buf[i]=letters[randGen.nextInt(71)];
           }
           return new String(buf);
      }
      //
}</pre>