import java.io.*;

class UseCharListsA7
{
// Shows constructive append and change on lists

 public static void main(String[] args) throws IOException
 {
  BufferedReader in = new BufferedReader(
                        new InputStreamReader(System.in));
  CharListA L1=null,L2=null,L3;
  char ch1,ch2;
  try {
       System.out.print("Enter first list of characters: ");
       L1 = CharListAIO.read(in);
       System.out.print("Enter second list of characters: ");
       L2 = CharListAIO.read(in);
      }
  catch(ListFormatException e)
      {
       System.out.println("Error: "+e.getMessage());
      }
  System.out.print("The lists are: ");
  CharListAIO.print(L1);
  System.out.print(" and ");
  CharListAIO.print(L2);
  System.out.println();
  System.out.println("Call constructive append ");
  L3=conAppend(L1,L2);
  System.out.print("The lists are now: ");
  CharListAIO.print(L1);
  System.out.print(" and ");
  CharListAIO.print(L2);
  System.out.print(" and ");
  CharListAIO(L3);
  System.out.println();
  System.out.print("Enter first character: ");
  ch1=in.readLine().charAt(0);
  System.out.print("Enter second character: ");
  ch2=in.readLine().charAt(0);
  System.out.print("Call constructive change of first to ");
  System.out.println("second character");
  System.out.println("in second list ");
  L3=conChange(ch1,ch2,L2);
  System.out.print("The lists are now: ");
  CharListAIO.print(L1);
  System.out.print(" and ");
  CharListAIO.print(L2);
  System.out.print(" and ");
  CharListAIO.print(L3);
  System.out.println();
 }

 public static CharListA conAppend(CharListA L1,CharListA L2)
 {
  if(L1==null)
     return L2;
  else
     {
      CharListA L3 = conAppend(L1.tail,L2);
      return new CharListA(L1.head,L3);
     }
 }

 public static CharListA conChange(char ch1,char ch2,CharListA L)
 {
  if(L==null)
     return null;
  else 
     {
      CharListA T=conChange(ch1,ch2,L.tail);
      char h=L.head;
      if(h==ch1)
         return new CharListA(ch2,T);
      else
         return new CharListA(h,T);
     }
 }

}