Generating 8-character only UUIDs

Question

UUID libraries generate 32-character UUIDs.

I want to generate 8-character only UUIDs, is it possible?

Answer 1

I do not think that it is possible but you have a good workaround.

1. cut the end of your UUID using substring()
2. use code new Random(System.currentTimeMillis()).nextInt(99999999); this will generate random ID up to 8 characters long.

3. generate alphanumeric id:

   char[] chars = "abcdefghijklmnopqrstuvwxyzABSDEFGHIJKLMNOPQRSTUVWXYZ1234567890".toCharArray();
   Random r = new Random(System.currentTimeMillis());
   char[] id = new char[8];
   for (int i = 0;  i < 8;  i++) {
       id[i] = chars[r.nextInt(chars.length)];
   }
   return new String(id);
   

Answer 2

It is not possible since a UUID is a 16-byte number per definition. But of course, you can generate 8-character long unique strings (see the other answers).

Also be careful with generating longer UUIDs and substring-ing them, since some parts of the ID may contain fixed bytes (e.g. this is the case with MAC, DCE and MD5 UUIDs).