hi Guys: 
I am building a product that can update the Arduino program through double clicking the application icon. I have through about using processing to update the Arduino sketch, but other people from the forum said it's impossible. I wondering if there is another way to do it.
It's not clear what you're asking with respect to how Processing would be used to "update" it. Are you trying to reprogram the Arduino or just tweak various configuration values?
I am not sure which way is better. reprogram the Arduino IDE or using Processing to write an app that upload the new program to Arduino.
What I am trying to do is making a product that allow user to download firmware update from product website, once the new update is available. In this case I want to use Arduino, but it allows the new update to be uploaded to the device through executing the program which is Arduino based.