Updating file in java
Apache POI is a very good API , that can be handy in manipulating Excel documents.
This tutorial focuses on XLS documents (Office 97 – 2003). Iterator; public class update Excels I am an Oracle ACE in Oracle ADF/Webcenter.
I'm pretty sure all that stuff in math and dates is possible to do within oracle itself within SQL.
In general, if the question is about speed, my way is first to try in straightforward simplest way and then assess what kind of issues you are facing in the sense of timing the thing is that let's assume threads will be successful and with a lot of additional work may end up say in saving time let's say even two, or assuming a lot, three times but most probably would not end up in orders of magnitudes, whereas moving to PL/SQL from Java in many cases produces order of magnitude saving in time.
You have to close the document, and then "write" the update back to the same document.
That is the reason, why you need to close the Input Stream.
I need to decide as if i take either to do it on the database side or to do it externally via files, later i would not be able to turn back. You can devise some way to select and update grouped in certain chunks.
I don't see any reason why you can't have 4 different temp tables I would first start doing it without threads - it is additional complication - look at your times real life situations, if this is some application which you need to run once to update or you'll be using it all the time see how it goes first in termas of time especially if it ios mostly one time opperation- if you need it then think about threads @for_yan and @CEHJ: Thanks for the reply.
This would be a one time operation or load that i would be performing once in a few months.
What I thought was that I'll create 4 temp tables and distribute the total load in these 4 tables and simultaneously kick off 4 threads which would run simultaneously and load the data.
If threading would not be used then there is no reason for me to divide the load in 4 different tables.
What is the issue in using threads in the scenario explained. @for_yan: Basically I'll be taking about three fields which are the unique fields from each record and based on these three field values I'll be filling up the 52 columns which were empty before from 2 different tables.