Though it’s not unlikable, John Singleton’s second feature (Boyz N the Hood was his first) is an unholy mess in almost every respect. There’s a line in the final credits saying that, for the purposes of copyright, Columbia Pictures is the author of this film, so maybe Columbia and not Singleton should be held accountable for the meandering and badly told (if occasionally suggestive) love story about a hairdresser-poet (Janet Jackson) and a postman (Tupac Shakur) from South Central LA who take a trip up to Oakland in a mail truck with another couple, bringing all their ghetto-bred problems with them. The title comes from the poet’s name, Justice, and though Jackson shows a lot of charm in the role, it’s often hard to relate the poetry she’s supposed to have written (which is read mainly offscreen) to her character. (In fact, the poems are by Maya Angelou, who’s around to play a bit part.) After a deceptively funny and offbeat beginning, the movie keeps restarting; each new start shows some promise, and Singleton’s talent never really deserts himbut the parts don’t come together to create a unified story. With Regina King, Joe Torry, Roger Guenveur Smith, and Tyra Ferrell. (JR)