asked on

Multithreading Problem

I multithread a process for each record returned from the query.
The problem is that I call addToFinalLetter() as each job completes.
I actually need to make sure that addToFinalLetter() in the order the query returns the records so that they are in the correct order.
I'm having a hard time explaining what I mean, so if anybody has any idea what I'm talking about or questions.. I would appreciate any help.

Thanks!

Tom

public void run()
{
try
{
workers = new ArrayList();

for ( int i = 0; i < simulWorkers; i++ )
{
workers.add( i, new Worker( getNextLogSeqno(), printSeqno, dbName, imageDbName, userId ) );
((Worker) workers.get( i ) ).start();
}

while ( completed < letterCount )
{
for ( int i = 0; i < simulWorkers; i++ )
{
worker = ((Worker) workers.get( i ) );

if ( worker.isDone() )
{
worker.done = false;

addToFinalLetter( worker.getLetter() );

completed++;

logSeqno = getNextLogSeqno();

if ( logSeqno != 0 )
{
workers.set( i, new Worker( logSeqno, printSeqno, dbName, imageDbName, userId ) );

((Worker) workers.get( i ) ).start();
}
}
}
}

workers = null;

done = true;
}
catch ( Exception ignore ) {}
}

SOLUTION

CEHJ

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NorCal19

ASKER

Can you please show me an example of how this would work?

I tried briefly to use the wait and notify but I kept getting some ObjectMonitorException....

Thanks,

Tom

ASKER CERTIFIED SOLUTION

JugglerW

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NorCal19

ASKER

I actually ended up doing it in a really ghetto way:

I first loop through the query and load the logSeqnos into an ArrayList I call sequence. This will be the order I must append them later.

Then, I also have a HashMap called dataPairs that is populated as each worker completes. The key for the HashMap is the log seqno and the value is the object that I pass to the append method.

So once all workers have completed I can run the following:

private void createDocument()
{
try
{
for ( int i = 0; i <= sequence.size(); i++ )
{
finalLetter.appendDocument((Letter) dataPairs.get( sequence.get( i ) ) );
}
}
catch ( Exception ignore ) {}
}

Thank you both for your help.

I will split the points evenly

CEHJ

:-)