Will there be an app for pottermore on iphone?

I don't have a computer and I can't play on the browser because iphone won't support java I guess.

Why don't you get hold of the developer and msg them to see if there developing the game for mobile.

No plans for an app have been announced. However, if you have a tablet of some sort, you should be able to use Pottermore on that. (See http://insider.pottermore.com/2013/11/pottermorecom-at-your-fingertips_14.html ).

You can also keep checking the Pottermore Insider to see if they ever announce it in the future. http://insider.pottermore.com/