Hello I have created an aplication in android builder using admob ads.But admob ads are not showing in my app,Please help 
Are you tried with test ads ? Is your app published on appstore, is your app approved by admob ?
It’s depends on your ads implementation. After ad dismissed you need to load again to show ad. Share blocks images with us for more info.
I think It’s violating google ads policy…
Ooh! Where you know about this😅. If you think to show ads with single loading then you can try. All the ads need to load again after they dismissed, otherwise no ads showing in app.
If you are loading ads multiple times without showing (or dismissed) then it’s probably violation of policy.
Where are you read this article on by google admob?
You can try yourself. A single load of ads doesn’t shows many times.
I don’t know where I read, but I’m pretty sure it’s not a violation of policy. If you need more information then go to admob privacy policy page.
The actual violation is loading ads many times without dismissed by the user. It will increase the request rate but very low impression.