EDIT

import java.util.ArrayList;

import java.util.List;

import org.eclipse.equinox.internal.p2.ui.ProvUI;

import org.eclipse.equinox.internal.p2.ui.model.ElementUtils;

import org.eclipse.equinox.internal.p2.ui.model.MetadataRepositoryElement;

import org.eclipse.equinox.p2.repository.IRepository;

import org.eclipse.equinox.p2.repository.IRepositoryManager;

import org.eclipse.equinox.p2.repository.metadata.IMetadataRepositoryManager;

import org.eclipse.equinox.p2.ui.ProvisioningUI;

import eu.etaxonomy.taxeditor.preference.PreferencesUtil;

    /**

     * Retrieve and load the saved list of repositories from the preference store,

     * making sure that at least the default repository is always loaded.

     */

    @SuppressWarnings("restriction")

    public static void setP2UpdateRepositories() {

        List<MetadataRepositoryElement> repoElements = new ArrayList<MetadataRepositoryElement>();

        List<MetadataRepositoryElement> savedRepoElements = new ArrayList<>();

        MetadataRepositoryElement mre = new MetadataRepositoryElement(null, getP2UpdateRepository(), true);

        mre.setNickname(getP2UpdateRepositoryName());

        savedRepoElements.add(mre);

        repoElements.addAll(savedRepoElements);

        ElementUtils.updateRepositoryUsingElements(ProvisioningUI.getDefaultUI(),repoElements

                .toArray(new MetadataRepositoryElement[]{} ));

    }

    public static String getP2UpdateRepositoryName(){

        return ApplicationUtil.isStable()?EDIT_STABLE_UPDATE_SITE_NAME:EDIT_NIGHTLY_UPDATE_SITE_NAME;

    }

    /**

     * {@link org.eclipse.equinox.p2.ui.RepositoryManipulationPage} which handles the repsitory site list

     * in preferences does not create a preference store and hence the changes are not saved. This means

     * that we need to save it ourselves.

     *

     * This method saves the list of current repositories in the preference store as a string with

     * specific delimiters.

     */

    public static void saveP2RepositoryPreferences() {

        IMetadataRepositoryManager metaManager = ProvUI.getMetadataRepositoryManager(ProvisioningUI.getDefaultUI().getSession());

        URI[] currentlyEnabled = metaManager.getKnownRepositories(IRepositoryManager.REPOSITORIES_ALL);

        URI[] currentlyDisabled = metaManager.getKnownRepositories(IRepositoryManager.REPOSITORIES_DISABLED);

        List<MetadataRepositoryElement> repoElements = new ArrayList<MetadataRepositoryElement>();

        for(URI repo : currentlyEnabled) {

            boolean enabled = true;

            String nickname = metaManager.getRepositoryProperty(repo, IRepository.PROP_NICKNAME);

            MetadataRepositoryElement element = new MetadataRepositoryElement(null, repo, true);

            element.setNickname(nickname);

            element.setEnabled(enabled);

            repoElements.add(element);

        }

        for(URI repo : currentlyDisabled) {

            boolean enabled = false;

            String nickname = metaManager.getRepositoryProperty(repo, IRepository.PROP_NICKNAME);

            MetadataRepositoryElement element = new MetadataRepositoryElement(null, repo, true);

            element.setNickname(nickname);

            element.setEnabled(enabled);

            repoElements.add(element);

        }

        PreferencesUtil.setP2Repositories(repoElements);

    }