Útil para validação de códigos GTIN, aplicado cálculos baseado no GS1.

GTINUtil.java

import lombok.AccessLevel;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.RequiredArgsConstructor;

import java.util.Arrays;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

/**
 *
 * @author Rodrigo Cananea <rodrigoaguiar35@gmail.com>
 */
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class GTINUtil {

    private static final String SEM_GTIN = "SEM GTIN";

    public static boolean isGTIN(int gtin) {
        return gtin == 8 || gtin == 12 || gtin == 13 || gtin == 14;
    }

    public static boolean isGTIN(String barras) {
        if (barras == null) return false;
        String numeric = barras.replaceAll("\\D", "");
        int length = numeric.length();
        return length >= 8 && length <= 14 && validaPrefixos(barras);
    }

    public static boolean isValido(String barras) {
        return !SEM_GTIN.equals(validar(barras));
    }

    public static String validar(String barras) {
        if (!isGTIN(barras)) {
            return SEM_GTIN;
        }
        GTINEnum gtinEnum = GTINEnum.get(barras.replaceAll("\\D", "").length());
        return validar(barras, gtinEnum);
    }

    public static String validar(String barras, GTINEnum gtinEnum) {
        if (isGTIN(barras) && isGTIN(gtinEnum.getCodigo())) {
            switch (gtinEnum) {
                case GTIN8:  return validaGTIN(barras, Arrays.asList(0, 2, 4, 6));
                case GTIN12: return validaGTIN(barras, Arrays.asList(0, 2, 4, 6, 8, 10));
                case GTIN13: return validaGTIN(barras, Arrays.asList(1, 3, 5, 7, 9, 11));
                case GTIN14: return validaGTIN(barras, Arrays.asList(0, 2, 4, 6, 8, 10, 12));
                default:     return SEM_GTIN;
            }
        }
        return SEM_GTIN;
    }

    private static String validaGTIN(String barras, List<Integer> indices) {
        List<Integer> barrasArray = Arrays.stream(barras.split(""))
                .map(Integer::valueOf)
                .collect(Collectors.toList());

        AtomicInteger soma = new AtomicInteger(0);
        IntStream.range(0, barrasArray.size() - 1).forEach(i -> {
            int n = barrasArray.get(i);
            if (indices.contains(i)) {
                n *= 3;
            }
            soma.addAndGet(n);
        });

        int multiplo = obterMultiploDeDez(soma.get());
        int resultado = multiplo - soma.get();
        boolean isValido = resultado == barrasArray.get(barrasArray.size() - 1);

        return isValido ? barras : SEM_GTIN;
    }

    /**
     * Múltiplo mais próximo, igual ou superior de dez
     * https://www.gs1.org/services/how-calculate-check-digit-manually
     *
     * @param soma
     * @return
     */
    private static int obterMultiploDeDez(int soma) {
        return (soma % 10 == 0 ? soma : (soma - (soma % 10)) + 10);
    }

    /**
     * Validar prefixos validos de acordo com:
     * https://www.gs1.org/standards/id-keys/company-prefix
     *
     * @param barras
     * @return
     */
    public static boolean validaPrefixos(String barras) {
        return Arrays.stream(GS1Prefixo.values())
                .anyMatch(gs1 -> Pattern.compile(gs1.getPrefixos()).matcher(barras).find());
    }

    @Getter
    @RequiredArgsConstructor
    public enum GS1Prefixo {
        GS1_US("^(001|019|030|039|050|059|060|139)"),
        GS1_FRANCE("^(300|379)"),
        GS1_BULGARIA("^(380)"),
        GS1_SLOVENIJA("^(383)"),
        GS1_CROATIA("^(385)"),
        GS1_BIH("^(387)"),
        GS1_MONTENEGRO("^(389)"),
        GS1_GERMANY("^(400|440)"),
        GS1_JAPAN("^(450|459|490|499)"),
        GS1_RUSSIA("^(460|469)"),
        GS1_KYRGYZSTAN("^(470)"),
        GS1_CHINESE_TAIPEI("^(471)"),
        GS1_ESTONIA("^(474)"),
        GS1_LATVIA("^(475)"),
        GS1_AZERBAIJAN("^(476)"),
        GS1_LITHUANIA("^(477)"),
        GS1_UZBEKISTAN("^(478)"),
        GS1_SRI_LANKA("^(479)"),
        GS1_PHILIPPINES("^(480)"),
        GS1_BELARUS("^(481)"),
        GS1_UKRAINE("^(482)"),
        GS1_TURKMENISTAN("^(483)"),
        GS1_MOLDOVA("^(484)"),
        GS1_ARMENIA("^(485)"),
        GS1_GEORGIA("^(486)"),
        GS1_KAZAKSTAN("^(487)"),
        GS1_TAJIKISTAN("^(488)"),
        GS1_HONG_KONG("^(489)"),
        GS1_UK("^(500|509)"),
        GS1_GREECE("^(520|521)"),
        GS1_LEBANON("^(528)"),
        GS1_CYPRUS("^(529)"),
        GS1_ALBANIA("^(530)"),
        GS1_MACEDONIA("^(531)"),
        GS1_MALTA("^(535)"),
        GS1_IRELAND("^(539)"),
        GS1_BELGIUM_LUXEMBOURG("^(540|549)"),
        GS1_PORTUGAL("^(560)"),
        GS1_ICELAND("^(569)"),
        GS1_DENMARK("^(570|579)"),
        GS1_POLAND("^(590)"),
        GS1_ROMANIA("^(594)"),
        GS1_HUNGARY("^(599)"),
        GS1_SOUTH_AFRICA("^(600|601)"),
        GS1_GHANA("^(603)"),
        GS1_SENEGAL("^(604)"),
        GS1_OMAN("^(607)"),
        GS1_BAHRAIN("^(608)"),
        GS1_MAURITIUS("^(609)"),
        GS1_MOROCCO("^(611)"),
        GS1_ALGERIA("^(613)"),
        GS1_NIGERIA("^(615)"),
        GS1_KENYA("^(616)"),
        GS1_CAMEROON("^(617)"),
        GS1_COTE_D_IVOIRE("^(618)"),
        GS1_TUNISIA("^(619)"),
        GS1_TANZANIA("^(620)"),
        GS1_SYRIA("^(621)"),
        GS1_EGYPT("^(622)"),
        GS1_LIBYA("^(624)"),
        GS1_JORDAN("^(625)"),
        GS1_IRAN("^(626)"),
        GS1_KUWAIT("^(627)"),
        GS1_SAUDI_ARABIA("^(628)"),
        GS1_EMIRATES("^(629)"),
        GS1_NAMIBIA("^(631)"),
        GS1_FINLAND("^(640|649)"),
        GS1_CHINA("^(680|681|690|699)"),
        GS1_NORWAY("^(700|709)"),
        GS1_ISRAEL("^(729)"),
        GS1_SWEDEN("^(730|739)"),
        GS1_GUATEMALA("^(740)"),
        GS1_EL_SALVADOR("^(741)"),
        GS1_HONDURAS("^(742)"),
        GS1_NICARAGUA("^(743)"),
        GS1_COSTA_RICA("^(744)"),
        GS1_PANAMA("^(745)"),
        GS1_DOMINICAN_REPUBLIC("^(746)"),
        GS1_MEXICO("^(750)"),
        GS1_CANADA("^(754|755)"),
        GS1_VENEZUELA("^(759)"),
        GS1_SWITZERLAND("^(760|769)"),
        GS1_COLOMBIA("^(770|771)"),
        GS1_URUGUAY("^(773)"),
        GS1_PERU("^(775)"),
        GS1_BOLIVIA("^(777)"),
        GS1_ARGENTINA("^(778|779)"),
        GS1_CHILE("^(780)"),
        GS1_PARAGUAY("^(784)"),
        GS1_ECUADOR("^(786)"),
        GS1_BRASIL("^(789|790)"),
        GS1_ITALY("^(800|839)"),
        GS1_SPAIN("^(840|849)"),
        GS1_CUBA("^(850)"),
        GS1_SLOVAKIA("^(858)"),
        GS1_CZECH("^(859)"),
        GS1_SERBIA("^(860)"),
        GS1_MONGOLIA("^(865)"),
        GS1_NORTH_KOREA("^(867)"),
        GS1_TURKEY("^(868|869)"),
        GS1_NETHERLANDS("^(870|879)"),
        GS1_SOUTH_KOREA("^(880|881)"),
        GS1_MYANMAR("^(883)"),
        GS1_CAMBODIA("^(884)"),
        GS1_THAILAND("^(885)"),
        GS1_SINGAPORE("^(888)"),
        GS1_INDIA("^(890)"),
        GS1_VIETNAM("^(893)"),
        GS1_PAKISTAN("^(896)"),
        GS1_INDONESIA("^(899)"),
        GS1_AUSTRIA("^(900|919)"),
        GS1_AUSTRALIA("^(930|939)"),
        GS1_NEW_ZEALAND("^(940|949)"),
        GS1_MALAYSIA("^(955)"),
        GS1_MACAU("^(958)");

        private final String prefixos;
    }

    @Getter
    @RequiredArgsConstructor
    public enum GTINEnum {

        SEM_GTIN(0),
        GTIN8(8),
        GTIN12(12),
        GTIN13(13),
        GTIN14(14);

        private final Integer codigo;

        public static GTINEnum get(int codigo) {
            return Arrays.stream(GTINEnum.values())
                    .filter(enums -> enums.getCodigo() == codigo)
                    .findFirst()
                    .orElse(GTINEnum.SEM_GTIN);
        }
    }

}