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I am not a thorough JAVA professional but have experience in Programming, none with threads though. I have an application code which currently does the following.

  1. Make connection with a DB
  2. Pull records from DB into a collection (Each record has an 'action code' 1-5 besides other things
  3. Each record is picked one by one and Based on each action code some particular method (One each for each action code ) is called from a class EVENTHANDLER.class
  4. These individual methods also use/share some other methodsin EVENTHANDLER.class and some other classes for some common functionality that there is
  5. Finally the db_sequence is updated
  6. All records processed so finish

Now , I have a requirement, which is little vague right now, but it wants the introduction of threads into above for primarily a performance enhancement. Along with prioritizing the process of some records with some specific action code above the others. for example- A record with Action code -2 should be on high prority over 1 and then 3 and then 4.

My question is to how to go about first with the approach to implement this. Secondly this is to be done in JAVA 1.6 so what classes should I use. Also any direction codewise (example code) or based on functional flow above would be greatly helpful.

A very direct question is- for the above action code (1-5) should I have five threads running concurrently in whole or should I have one thread for each record (there can be hundreds), irrespective of Action Code?

Thanks Already

user2043000
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    Is it possible to run two tasks at the same time? I mean, do you need to complete "task1" before you can start "task2"? Another question: those tasks are very long? are we talking about seconds, minutes or what? – Salvatorelab Feb 05 '13 at 12:48

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I'd be concerned if I were you or the person who asked you to do this.

Do you have numbers to show what the performance for the existing app is? If yes, do they exceed the target for the expected performance? I wouldn't make a judgment regarding threads until I had both.

Threading is an advanced topic that's easy to get wrong, even if you're experienced.

It sounds to me like the database portion can be a single thread. The handlers might be long-running, so I'd run those using Executor and the new constructs in the Java concurrency package. Under no circumstances should you do this with raw Threads.

It sounds to me like you'll need help. I'd find someone that knows Java better than you do to consult.

duffymo
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    People should not think so much in threads as in independent tasks or jobs. In this case, there seem to be jobs that could be submitted to a ThreadPoolExecutor constructed from a PriorityBlockingQueue. That queue should use the action code for sorting. Do your own testing to decide on the optimum level of concurrency for the thread pool. However, if this system hasn't been designed for multithreading, there is a good chance that the processing classes (EVENTHANDLER & friends) are not thread-safe. – Ralf H Feb 05 '13 at 13:10
  • Great points, Ralf H. I'd vote this up if it were an answer. – duffymo Feb 05 '13 at 13:15
  • Maybe you would, but there's an equal chance it would get a downvote if it's not complete enough or some other reason. So, if I don't have time enough, I comment only. Actually, the advice regarding threads/tasks come to mind a lot here, but it does not answer the question. – Ralf H Feb 05 '13 at 14:53
  • Yeah, I do the same thing. – duffymo Feb 05 '13 at 15:27