import java.util.*;

public abstract class BauholzCollection {
    private Set<Collection<? extends Bauholz>> woodPiles = new HashSet<>();

    protected void addWoodPileForPrintList(Collection<? extends Bauholz> pile){
        woodPiles.add(pile);

    }

    public void list(){


        for (Collection<? extends Bauholz > pile: woodPiles){

            for (Bauholz piece: pile){
                System.out.println("Length: " + piece.getLength());
            }
        }
    }
}