public ArrayList<Mapping> cloneFrame(){
  if (stack[top] == null)   return null;
  ArrayList<Mapping> clone=new ArrayList<Mapping>();
  for (Mapping map=topOfFrame(); map != null; map=next()) {
    clone.add(map);
  }
  return clone;
}

public ArrayList < Mapping > cloneFrame ( ) { if ( stack [ top ] == null ) return null ; ArrayList < Mapping > clone = new ArrayList < Mapping > ( ) ; for ( Mapping map = topOfFrame ( ) ; map != null ; map = next ( ) ) { clone . add ( map ) ; } return clone ; }
return a copy of the current frame . returns null if none are present .
