public BookData find(String query){
		BookData match = new BookData();
		
		//check each book in this BookData.
		//if it matches query, then add it to match
		for(int i=0; i<books.size();i++){
			if(books.get(i).matches(query)){
				match.addBook(books.get(i));
			}
		}
		return match;
	}