Re: Lazy initialization
On Jul 24, 9:39 am, Sreenivas <thatiparthysreeni...@gmail.com> wrote:
When is books (ArrayList ) object created ?
The Arraylist is a local variable. It is created on the call to
getBooks().
Is it fine to place getBooks() method in Book class?
It is probably not a good idea to place getBooks() as an instance
method in the Book class. In order to call it, you will need a Book
object. You would call it like this:
Book myBook = new Book("1234-45");
List<Book> list = myBook.getBooks();
Creating a dummy Book object to do this, doesn't make much sense.
The simplest modification would be to make that method static ( public
static List<Book> getBooks(){...} ) . As such it becomes something
like a helper method which can be called directly using code like
(note, we use the class the name before the dot):
List<Book> list = Book.getBooks();
On the other hand, you are writing about database connection etc. So
making the getBooks() call needs access to some information (database
name, login etc). In this case, it probably makes sense to create a
new class which handles this whole process.
I have a difficulty in understanding Lazy Initialization .
Lazy Initialization:
Lazy Initialization for List<Book> in getBooks() method is like this ,
if i am not wrong
public List<Book> getBooks()
{
List<Book> books;
if(books==null)
{
books = new ArrayLis=
t<Book>();
//Here goes code for maki=
ng database connection and loading Book
objects
//into ArrayList
}
return books;
}
This won't compile, as your local variable books has not been
initialized. What you probably want to do, is to have a member
variable which holds the books, so you can access that variable on
each call of getBooks() (possibly a static Field if you make your call
to getBooks() static, but I think that's a bad idea).
But, lazy initialization is an optimization. At the point where you
are, optimization is the last thing you should think about. First make
it work, then make it fast (if needed only).
I recommend that you read a book about Java to get the basic (like
static, member or local vars etc) before going on.
Best regards
Phil