Please find below a list of J adjectives which might be used to describe a person.
Positive
jolly
jovial
joyful
joyous
jubilant
just
Negative
jaded
jealous
juvenile
Other
jittery
jobless
jocular
jumpy
There are many more lists of adjectives on this website. For more adjectives starting in J, see this post containing a large number of adjectives beginning with the letter J, some of which can be used for describing people.
Did I miss any adjectives? Please add them here. Thanks.