It's required from me to make an android app that must
1\Displays the cheapest prizes for some goods eg car by parsing them from some commercial web sites ascending .
2\Alerts users with the updates in those web sites
I saw some android apps doing like this tasks (they enable users to be the first to know by sending them push notifications of breaking news events and so on)
for example Pulse app.
How they do this ? that is my problem
Perhaps you will advice me using rss feed but not all web sites have rss feed for just an example this website
please can anyone help
If it were me, I'd probably use python's BeautifulSoup to scour the websites for the data you need, and then I'd store that on my webserver in some easily Java-digestible form like JSON. (BeautifulSoup is a quite powerful screen scraper and there are a lot of examples on web as to how to use it.) Auto update it every 24 hours, or more frequently, depending on your requirements. Your Android app can then regularly query this data, and then generate the required notifications, etc. Alternatively, you can use the Android compatible library here that's supposedly similar to BeautifulSoup.