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Thread: How to use and notify

  1. #1
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    Default How to use and notify

    Dear all
    I have four classes that extends thread. the names are for example C1, C2, C3, C4. now these threads shares a linked list between each other. C1 writes data to a list and C2 reads from that list and writes to other list and C3 reads from that other list. now C4 executes the run() method for these threads like this:

    ...
    for(int i=0;i<Filters.size();i++)
       Filters.get(i).run();
    ...

    but the problem is that when C1 executes, it writes the data to list and after that C2 executes and reads that data. but C2 needs another data but in this state the list is empty. so C2 calls wait() and waits. but this leads to C3 not run. I want to continue running after C2 waits. I want to run C3 and after that C1 and so on

    but I don't know what is the problem when C2 waits, my all program waits!!!!!!!!!!!!!!!

    Please help me if there is a solution

    thanks: Saeid


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: How to use and notify

    How are you using the wait and notify methods?

  3. The Following User Says Thank You to Norm For This Useful Post:

    Saeid (August 12th, 2010)

  4. #3
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    Default Re: How to use and notify

    the method that writes into list, the list is called OutChannel

        	synchronized(OutChannel)
        	{
        		DataItem.DataField =Data;
        		DataItem.Valid=true;
     
                   OutChannel.Push(DataItem);
                   OutChannel.notify();
        	}

    and the method that reads from list, the list called InChannel

    		synchronized(InChannel)
    		{
     
    		    while(InChannel.Size()==0)
    			    try
    		        {
    			       InChannel.wait();
    			    }catch (InterruptedException e){}
    		    Poped=InChannel.Pop();
    		    System.out.println("Poped: " + Poped.DataField + "   " + Poped.Valid);
    		    if (!Poped.Valid)
    		    {
    			    return null;
    		    }
    		    else
    		        return (Poped.DataField);

    the names are different in threads C1 and C2, but both pointers points to one list, and these pointer are set in C4. in the above code if C2 executes InChannel.wait(), all my program waits. but I want just C2 waits and C4 runs the C3 after that C1 and again C2 and C3 and so on

  5. #4
    Super Moderator Norm's Avatar
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    Default Re: How to use and notify

    Do the variables: InChannel and OutChannel refer to the same object? wait and notify won't work if they are different objects.
    The use of wait and notify requires that they be used with the same object. Read the Object class doc for those two methods.

  6. The Following User Says Thank You to Norm For This Useful Post:

    Saeid (August 12th, 2010)

  7. #5
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    Default Re: How to use and notify

    OK. thanks