public static synchronized GlobalClass getInstance()
{
    if(instance==null)
    {
        instance=new GlobalClass();
    }
    return instance;
}

/**
 * @return This session's config data.
 */
public Config getConfig() {
    Config config = new Gson().fromJson(mPreferences.getString(KEY_CONFIG, null), Config.class);
    return config;
}

/**
 * Save this session's config data.
 *
 * @param config
 *            Config data.
 */
public void setConfig(Config config) {
    mPreferences.edit().putString(KEY_CONFIG, new Gson().toJson(config)).commit();
}

/**
 * @return Application configuration parameters.
 */
public static Config getConfig() {
    if (sConfig == null)
        sConfig = sPreferences.getConfig();
    return sConfig;
}

/**
 * Set application configuration parameters.
 *
 * @param config
 *            Config to set.
 */
public static void setConfig(Config config) {
    sPreferences.setConfig(config);
    sConfig = config;
}