public static String save(BookStoreItem[] inventory) throws IOException {
        final int BOOK = 0;
        final int CD = 1;
        final int DVD = 2;
        String saveMessage;
        boolean isSaved = false;
        File catalogFile = new File("catalog.txt");

        PrintWriter out = new PrintWriter (catalogFile);


            try {
                int index = 0;
                if (catalogFile.exists()!= true) {
                    throw new FileNotFoundException();
                }


                while (index < inventory.length) {
                    if (inventory[index] != null) {
                        if (inventory[index].getClass() == Book.class) {
                            out.println(BOOK);
                            out.println(inventory[index].getTitle());
                            out.println(inventory[index].getAuthor());
                            out.println(inventory[index].getPrice());
                            out.println(((Book)inventory[index]).getPages());

                        }
                        else if (inventory[index].getClass() == CD.class) {
                            out.println(CD);
                            out.println(inventory[index].getTitle());
                            out.println(inventory[index].getAuthor());
                            out.println(inventory[index].getPrice());
                            out.println(((CD)inventory[index]).getMinutes());
                            out.println(((CD)inventory[index]).getSeconds());

                        }
                        else {
                            out.println(DVD);
                            out.println(inventory[index].getTitle());
                            out.println(inventory[index].getAuthor());
                            out.println(inventory[index].getPrice());
                            out.println(((DVD)inventory[index]).getPlayingTime());

                        }//end of else

                    }//end of if statement.
                    index++;

                }//end of while loop
                isSaved = true;


                }//end of try
            catch(IOException ioe){
                throw ioe;
            }
            finally {
                if (isSaved = true) {
                saveMessage = "Saved to file";

                }//end of if
                else {
                    saveMessage = "Couldn't save to the file";

                }
                out.close();
            }

        return saveMessage;
    }//end of save()