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question about unique identity of record and lock

LianGuang Wang
Greenhorn

Joined: Mar 26, 2006
Posts: 11
// Reads a record from the file. Returns an array where each
// element is a record value.
public String[] read(int recNo) throws RecordNotFoundException;
what's the meaning of recNo?i think that is the position in the physical file.so it's not unique because this recNo can be reused.
so in the update synchronized block,we need to compare each field in the record to confirm the record state.and the client must send back all the field of the record which be booked?
It's truth? i want a Positive response! thanks!
Andrew Monkhouse
author and jackaroo
Marshal Commander

Joined: Mar 28, 2003
Posts: 11509
    
  95

Hello "Hot Strong"

Welcome to JavaRanch and this forum.

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Thanks, Andrew


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LianGuang Wang
Greenhorn

Joined: Mar 26, 2006
Posts: 11
i'm sorry for my inattention!
Animesh Saxena
Ranch Hand

Joined: Jan 15, 2006
Posts: 62
Can't understand ur question clearly.
recNo is just a number which indicates position of record. to get the actual record you use something like this

dbFile.seek((recNo-1) * recordLength);
keep the recordLength calculated in the beginning only.
assuming recNo starts from 1...
in update method when you pass the recNo seek the location of file using the above code and write the content in form of bytes.
if its a string then use.
dbFile.write(contentString.getBytes());


Animesh Saxena<br /> <br />Open Source Developer
 
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