Tarminder :
How & where to download java latest version on my smartphone ?
You were not very specific about your device or goal.
Generally speaking, smartphones do not support Java applets. A few do (Nokia N900), but most (other Nokia devices, Windows Phone, Android, iOS) do not support Java applets. Android supports Java applications written specifically for Android, but not general Java applications.
Edit: Actually, you can install Java (under real linux) in a chroot under Android.