class RandString{
static String base = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
static String get(int len){
StringBuffer buf = new StringBuffer(len);
while(buf.length() < len){
long n = Math.round(((Math.random() * 100)) % base.length());
buf.append(base.charAt((int)n));
}
return buf.toString();
}
}