生成随机数纯数字

/**
* 生成随机数纯数字
* @param length  // 随机数的长度
* @return
*/
public static String getRandom(int length) {
Random random = new Random();
String rr = "";
Set set = new HashSet();
while (set.size() < length) {
set.add(random.nextInt(10));
}
Iterator iterator = set.iterator();
while (iterator.hasNext()) {
rr = rr + iterator.next();
}
return rr;
}