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URLyBird Question

 
henry yeung
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I just download the URLyBird assignment(1.3.3)

There is some question.


1. Where is record number when read,update,lock,unlock and delete record since there is no a record number in the data file?

2. Is it directly access data file or load data to memory?

3. How to read,write,rewrite data file?

4. How to identify the record is unique?

5. explain data file format?

Thanks,

Henry
 
Paul Bourdeaux
Ranch Hand
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Hello Henry,

First, you need to change your name to comply with the JavaRanch Naming Policy. Second, I would recommend taking some time and looking through some of the posts in this forum. Many of your questions have been asked and answered in other threads. Here are some short answers to get you started...

1. Where is record number when read,update,lock,unlock and delete record since there is no a record number in the data file?
There is no actual record number in the data file. Most people use the record's relative location as the record number (i.e. the first record in the data file is number 1, second is number 2...).

2. Is it directly access data file or load data to memory?
Either. Search this forum for "cache" and you will turn up many threads advocating each side. You just have to document your choice in you choices.txt

3. How to read,write,rewrite data file?
Ummm, that is actually a pretty integral part of the assignment, and you should at least try to come up with a solution before asking how it is done. If you need a starting point, search through this forum, or pick up a copy of Max's Book.

4. How to identify the record is unique?
In the B&S assignment, some people identify a primary key. In the URLyBird assignment, there isn't any candidate keys except for the entire record. Most people appear to have used the record number instead of any key. Search this forum for "DuplicateKeyException" and you will see a whole host of threads dealing with the subject.

5. explain data file format?
The data file is a flat file. RandomAccessFile seems to be the most popular way to read it into your application. Your instructions detail the schema format of the file.

Hope that helps, and good luck with your assignment!
 
henry yeung
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Thanks your reply ,Paul Bourdeaux
 
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