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Objects have to be considered in real-time scenarios. They have State, Behavior, Identity & Responsibility.
Since you have given a brief idea on what you want to do, I would suggest to break up your system into smaller parts and identify the actors in the system. When I say actors think of them as live beings or in a more sophisticated language, personify them.
From what you said, I guess you can use the same queryManager object, or else you can use static-synchronized methods for database operation, again completely depends upon your scenario.
Don't walk as if you rule the world, walk as if you don't care who rules it...
I don't think we can tell from what you have said whether you want several objects or one object used repeatedly.
Have a look through all the methods in your classes, and see whether there are any methods which do not query access or use any information from the object. Then see whether any of those methods do not alter record or enter any information into the object. You may do well to convert those methods to static methods, which belong to the class, and are best called without an object being created at all.
There are some more issues which you need to consider when you are using same objects and you are also doing database operations here. So while updating, etc. you might be faced with synchronization issues. Consider these while designing your application - though your application might seem safe, at some point it might break and you'd wonder what went wrong
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