import Java.util.Random;

class SomeBizOperation {

 /*疯狂到令人发指*/
 public String getNewId() {

 while (true) {
 String id = newId(10);
 var obj = SomeTableQuery.getById(id);
 if (obj == null) {
 return obj;
 }
 }
 }

 private String newId(int length) {
 String str = "0123456789";
 var random = new Random();
 StringBuffer sb = new StringBuffer();
 for (int i =0; i<length; i++){
 int number = random.next(62);
 sb.append(str.charAt(number));
 }
 return sb.toString();
 }
}