生成19位UUID

public static String getUuid() {
        UUID uuid = UUID.randomUUID();
        StringBuilder sb = new StringBuilder();
        sb.append(digits(uuid.getMostSignificantBits() >> 32, 8));
        sb.append(digits(uuid.getMostSignificantBits() >> 16, 4));
        sb.append(digits(uuid.getMostSignificantBits(), 4));
        sb.append(digits(uuid.getLeastSignificantBits() >> 48, 4));
        sb.append(digits(uuid.getLeastSignificantBits(), 12));
        return sb.toString();
    }