public Dependencies add(Dependency dependency){
  dependencies.add(requireNonNull(dependency,"Required not null dependency"));
  if (!isNew()) {
    addDependencyToXML(dependency);
  }
  return this;
}

public Dependencies add ( Dependency dependency ) { dependencies . add ( requireNonNull ( dependency , "Required not null dependency" ) ) ; if ( ! isNew ( ) ) { addDependencyToXML ( dependency ) ; } return this ; }
adds new dependency to the end of dependencies list . < p / > creates dependencies tag if element doesn ' t have dependencies yet
