Generate Long ID from UUID

UniqueId.java

    /**
     * Genereate unique ID from UUID in positive space
     * Reference: http://www.gregbugaj.com/?p=587
     * @return long value representing UUID
     */
    private Long generateUniqueId()
    {
        long val = -1;
        do
        {
            final UUID uid = UUID.randomUUID();
            final ByteBuffer buffer = ByteBuffer.wrap(new byte[16]);
            buffer.putLong(uid.getLeastSignificantBits());
            buffer.putLong(uid.getMostSignificantBits());
            final BigInteger bi = new BigInteger(buffer.array());
            val = bi.longValue();
        } 
         // We also make sure that the ID is in positive space, if its not we simply repeat the process
        while (val < 0);
        return val;
    }

@uppersnatch no. UUID operates in a bigger space than Long so when you "trim" it down you lose information that could be used to "inflate" it back again into UUID.