UUIDGen.java

import java.util.UUID;
import java.time.Instant;
import java.util.Base64;
import java.nio.ByteBuffer;
import java.security.SecureRandom;

/**
AAABZxtu/zzQb1EQOg==:20
AAABZxtu/z1VAsQOvQ==:20
AAABZxtu/z3ckixveA==:20
AAABZxtu/z0h3qPaxg==:20
AAABZxtu/z1k3W2VLw==:20
AAABZxtu/z163jTH1Q==:20
AAABZxtu/z3i5m6qJA==:20
AAABZxtu/z226JKMSA==:20
AAABZxtu/z3SEQXPmQ==:20
AAABZxtu/z6hkC54bA==:20
 */
public class  UUIDGen {

  public static void main(String[] args) {
    for(int i = 0; i < 10; i++){
      final String s = gen();
      System.out.println(s + ":" + s.length());
    }
  }

  private static String gen(){
    final int LONG_SIZE = 8;
    final int RANDOM_BYTE = 7;
    final byte[] random = new byte[RANDOM_BYTE];
    new SecureRandom().nextBytes(random);


    final ByteBuffer buff = ByteBuffer.allocate(LONG_SIZE + RANDOM_BYTE);
    buff.putLong(Instant.now().toEpochMilli());
    buff.put(random);

    final String s = Base64.getEncoder().encodeToString(buff.array());
    return s;
  }

}