Disposing Document objects
you no longer require a Document object, it is
recommended that you dispose of it by invoking its dispose method.
Each Document object consumes a file descriptor
and as much as 75 MB of RAM space on your application’s host platform.
If a Document object is not disposed, then the
Java Garage collection process disposes it. However, by disposing
of it sooner by using the dispose method, you can
free the memory occupied by the Document object.