public BrdLayerStructure(Collection<DsnLayer> p_layers){
  layers_list=new ArrayList<BrdLayer>(p_layers.size());
  for (  DsnLayer a_layer : p_layers) {
    layers_list.add(new BrdLayer(a_layer.layer_no,a_layer.name,a_layer.is_signal));
  }
  Collections.sort(layers_list);
}

public BrdLayerStructure ( Collection < DsnLayer > p_layers ) { layers_list = new ArrayList < BrdLayer > ( p_layers . size ( ) ) ; for ( DsnLayer a_layer : p_layers ) { layers_list . add ( new BrdLayer ( a_layer . layer_no , a_layer . name , a_layer . is_signal ) ) ; } Collections . sort ( layers_list ) ; }
you must guarantee that the collection has layer_no from zero onward without holes ! ! !
