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From Peter Firmstone <j...@zeus.net.au>
Subject Re: TaskManager requirements
Date Sun, 18 Jul 2010 02:49:04 GMT
Sounds like a good optimisation, I'm for it.  I agree, don't but all the 
tasks in the HashSet, just those you don't want duplicated.

Patricia Shanahan wrote:
> TaskManager has a method addIfNew(Task t) that adds a Task if, and 
> only if, there is no existing task that it equals, according to 
> .equals comparison.
>
> It has one existing use, adding an AddressTask in 
> com.sun.jini.reggie.RegistrarImpl. All instances of AddressTask are 
> added using addIfNew. AddressTask is final, and an AddressTask 
> considers itself equal only to other instances of AddressTask.
>
> I would like to modify TaskManager so that addIfNew adds the new Task 
> unless there is an equal Task that was also added using addIfNew. The 
> new javadoc comment would read:
>
>     /**
>      * Add a new task if it is not equal (using the equals method)
>      * to any existing active or pending task that was also added
>      * by this method.
>      */
>
> This permits a very simple implementation that does not depend on an 
> O(n) scan of all existing tasks. addIfNew would add the Task to a 
> HashSet<Task>, and do the rest of the processing if, and only if, the 
> HashSet add method returns true. I would remember if a particular Task 
> came through addIfNew, and if it did it will be removed from the 
> HashSet on completion or removal.
>
> This implementation would fully meet the needs of the existing use, at 
> least once I improve the hashCode method in AddressTask.
>
> The problem with putting all added Task instances in the HashSet is 
> that the add method permits addition of multiple tasks that equal each 
> other. I could work around that problem, but it would make the code 
> significantly more complicated, and add work to the normal case of 
> unconditionally added tasks.
>
> Patricia
>


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