EDIT

import java.util.ArrayList;

import java.util.UUID;

import org.apache.commons.lang.StringUtils;

import eu.etaxonomy.cdm.persistence.dto.TermDto;

import eu.etaxonomy.taxeditor.preference.LocalOrDefaultEnum;

import eu.etaxonomy.taxeditor.preference.PreferencesUtil;

import eu.etaxonomy.taxeditor.store.CdmStore;

    @Override

    public boolean performOk() {

        if (!isApply()){

            return true;

        }

        Object[] checkedElements = treeComposite.getViewer().getCheckedElements();

        List<UUID> listUIIDChecked = new ArrayList<>();

        List<TermDto> preferredTerms = new ArrayList<>();

        for (Object o : checkedElements) {

            if(o instanceof TermDto){

                TermDto termDto = (TermDto) o;

                listUIIDChecked.add(termDto.getUuid());

                preferredTerms.add(termDto);

            }

        }

        String saveCheckedElements = StringUtils.join(listUIIDChecked, ";"); //$NON-NLS-1$

        PreferencesUtil.setStringValue(PreferencePredicate.NameTypeDesignationStatus.getKey(), saveCheckedElements);

        String text = this.useLocalOrAdmin.getText();

        if (text.equals(LocalOrDefaultEnum.Database.getLabel()) || text.equals(LocalOrDefaultEnum.Default.getLabel())){

            PreferencesUtil.setBooleanValue(PreferencesUtil.createOverridePreferenceString(PreferencePredicate.NameTypeDesignationStatus.getKey()), false);

        }else if (text.equals(LocalOrDefaultEnum.Local.getLabel())){

            PreferencesUtil.setBooleanValue(PreferencesUtil.createOverridePreferenceString(PreferencePredicate.NameTypeDesignationStatus.getKey()), true);

        }

        CdmStore.getTermManager().setPreferredTermsByType(preferredTerms, TermType.NameTypeDesignationStatus);

        PreferencesUtil.firePreferencesChanged(this.getClass());

        return true;

    }