Java program to generate a unique and random six alpha numeric code

Question

I need to generate a reservation code of 6 alpha numeric characters, that is random and unique in java.

Tried using UUID.randomuuid().toString(), However the id is too long and the requirement demands that it should only be 6 characters.

What approaches are possible to achieve this?

Just to clarify, (Since this question is getting marked as duplicate). The other solutions I've found are simply generating random characters, which is not enough in this case. I need to reasonably ensure that a random code is not generated again.

Answer 1

Consider using the hashids library to generate salted hashes of integers (your database ids or other random integers which is probably better).

http://hashids.org/java/

Hashids hashids = new Hashids("this is my salt",6);
String id = hashids.encode(1, 2, 3);
long[] numbers = hashids.decode(id);