class IdentifiableObjectUtils {

    public static String join( Collection<? extends IdentifiableObject> objects )
    {
        if ( objects == null || objects.isEmpty() )
        {
            return null;
        }
        
        List<String> names = objects.stream().map( IdentifiableObject::getDisplayName ).collect( Collectors.toList() );
        return StringUtils.join( names, SEPARATOR_JOIN );
    }

}