“XX/XY” features some of the least interesting characters in the world, complaining about their problems in a way that makes you stop wondering why people think Gen Xers do nothing but whine. It’s a go-nowhere, do-nothing movie.

It begins in 1993 at Sarah Lawrence College, where free spirit artist Coles (Mark Ruffalo) meets and falls into bed with lady friends Sam (Maya Stange) and Thea (Kathleen Robertson). Coles and Sam eventually pair off, but their relationship is superficial and often centered on drinking, as is Thea’s relationship with hapless nice guy Sid (Kel O’Neill). Hey, it’s college, and people act crazy.

Skip ahead to the present. Sam and Thea have kept in touch, but neither has seen Coles in years. Turns out he’s a successful animator for an ad agency and lives with his girlfriend Claire (Petra Wright). Thea is married to a restaurateur, and Sam has just broken off an engagement with a Brit. The three old college chums meet up, and the sparks between Sam and Coles start to rekindle.

Coles, however, does not seem to have grown up much since college. In fact, he might be more of a selfish, immature pig now than he was then.

A movie whose point is that you have to grow up eventually runs the risk of featuring a character whose immaturity is annoying. Writer/director Austin Chick falls prey to this trap, though I suspect Mark Ruffalo’s infuriating childish smugness contributes, too.

The scenes taking place in the present are far more enjoyable than the college ones, but it’s still cheap, unengaging stuff. The humor is hit-or-miss, the drama is spotty, and the characters — did I mention this? — don’t inspire much concern. It is not boring, exactly, but it offers little reason to continue watching it beyond the frequent sex scenes.

C (; R, very strong sexuality and nudity, frequent harsh profanity.)