//to represent a nonempty list of ImageFile objects
class ConsList implements AList{

  ImageFile first;
  AList rest;

  ConsList(ImageFile first, AList rest){
    this.first=first;
    this.rest=rest;
  }

  //does this non-empty list contain that ImageFile   
  public boolean contains(ImageFile that){ 
    if (this.first.sameImageFile(that))
      return true;
    else 
      return this.rest.contains(that); 
  } 
}