Translate English to Latin

Amo J

A note about the letter 'J':
There was no letter 'J' in the Latin language until the Middle Ages, and then it
was used as an alternate form of the letter 'I'. It replaced 'I' when 'I' was used as
a consonant such as at the start of the name "Iulius".

In your request, I assume 'J' is the initial of the object of your affections and so I
would leave it as is.