EDIT

import java.util.HashSet;

import java.util.Set;

		result &= checkMissingExplicitSources(config);

    //******************************** CHECK *************************************************

    /**

     * @param config

     * @return

     */

    private boolean checkMissingExplicitSources(BerlinModelImportConfigurator config) {

        try {

             boolean result = true;

            Source source = config.getSource();

            String sql = " SELECT occ.OccurrenceId, occ.Sources, ocs.OccurrenceSourceId, ocs.SourceNumber, ar.EMCode, ar.Unit, n.FullNameCache, occ.PTRefFk  " +

                " FROM emOccurrence occ " +

                    " INNER JOIN emArea ar ON occ.AreaFk = ar.AreaId " +

                    " INNER JOIN PTaxon pt ON occ.PTNameFk = pt.PTNameFk AND occ.PTRefFk = pt.PTRefFk " +

                    " INNER JOIN Name n ON occ.PTNameFk = n.NameId  " +

                    " LEFT OUTER JOIN emOccurSumCat sumcat ON occ.SummaryStatus = sumcat.emOccurSumCatId " +

                    " LEFT OUTER JOIN emOccurrenceSource ocs ON occ.OccurrenceId = ocs.OccurrenceFk " +

                " WHERE ( occurrenceId IN ( SELECT occurrenceId FROM v_cdm_exp_occurrenceAll ))" +

                " ORDER BY occ.PTRefFk, n.fullNameCache, occ.occurrenceId";

            ResultSet rs = source.getResultSet(sql);

            int oldOccurrenceId = -1;

            Set<Integer> sources = new HashSet<>();

            int unmatched = 0;

            while (rs.next()){

                int occurrenceId = rs.getInt("OccurrenceId");

                if (occurrenceId != oldOccurrenceId){

                    checkExistingSources(sources, oldOccurrenceId, rs);

                    String sourcesStr = rs.getString("Sources");

                    sources = makeSources(sourcesStr);

                    oldOccurrenceId = occurrenceId;

                }

                String sourceIdStr = rs.getString("SourceNumber");

                Integer sourceId = StringUtils.isBlank(sourceIdStr) ? null: Integer.valueOf(sourceIdStr);

                unmatched = removeSource(sources, sourceId, occurrenceId, unmatched);

            }

            return result;

        } catch (Exception e) {

            e.printStackTrace();

            return false;

        }

    }

    /**

     * @param sources

     * @param sourceId

     * @param unmatched

     */

    private int removeSource(Set<Integer> sources, Integer sourceId, int occurrenceId, int unmatched) {

        boolean contained = sources.remove(sourceId);

        if (sourceId != null && !contained){

//            System.out.println("OccurrenceId(" + occurrenceId + "): sourceId " + sourceId + " not found in sources field.");

            unmatched++;

        }

        return unmatched;

    }

    /**

     * @param sources

     * @param occurrenceId

     * @param rs

     * @throws SQLException

     */

    private void checkExistingSources(Set<Integer> sources, int occurrenceId, ResultSet rs) throws SQLException {

        sources.remove(27133);

        sources.remove(0);

        if (!sources.isEmpty()){

            String emCode = rs.getString("EMCode").trim();

            String unit = rs.getString("Unit");

            String name = rs.getString("FullNameCache");

            String ref = rs.getString("PTRefFk");

            System.out.println(name + " ("+ ref + " (occId: " + occurrenceId + ", " + emCode + ", " + unit + "): The following sources are not matched: " + sources);

        }

    }

    private Set<Integer> makeSources(String sourcesStr) {

        Set<Integer> result = new HashSet<>();

        if (sourcesStr != null){

            String[] splits = sourcesStr.split("\\|");

            for (String split : splits){

                split = split.trim();

                if (StringUtils.isNotBlank(split)){

                    Integer number;

                    try {

                        number = Integer.valueOf(split);

                        result.add(number);

                    } catch (NumberFormatException e) {

                        e.printStackTrace();

                    }

                }

            }

        }

        return result;

    }