In the movie “Get Hard,” wealthy businessman James King — Will Ferrell — is wrongfully convicted of tax evasion. He hires his building's car-washer, Darnell Lewis — Kevin Hart, whom he incorrectly thinks has served time in jail, to teach him how to survive his upcoming 10-year prison sentence.

“Get Hard,” the prepping-for-prison would-be comedy from Will Ferrell and comedian-of-the-moment Kevin Hart, is about as funny as life imprisonment without the possibility of parole — or laughter.

Hart stars in a role that sounds similar to the one from his last film, “The Wedding Ringer,” in which he’s the black guy who has to teach the geeky white guy life lessons on how to survive an upcoming emotional upheaval.

In the prior movie, it was getting married, and in “Get Hard” it’s a 10-year stint in a max-security facility for corporate fraud and embezzlement.

The trouble is that Darnell (Hart), while living on the margins in South Central Los Angeles with his wife (Edwina Findley Dickerson) and daughter Makayla (Ariana Neal), doesn’t have so much as a traffic ticket to tarnish his record.

He runs a car-wash business in the building where successful Wall Street trader and unthinkingly racist James (Ferrell) works and becomes James’ go-to guy when the businessman realizes he’s being sent to the big house and doesn’t know how to toughen up to survive.

James turns to Darnell because he assumes the black man washing his car has a record and can teach him the ways of the cell block.

At first, Darnell balks but when James agrees to pay him $30,000, he plays along, promising to turn James from a smirking yuppie with a house in Bel-Air to a hardened convict with a “mad-dog” face. James’ mansion is refashioned into a makeshift prison, with his Hispanic household staff acting as fellow prisoners and guards, and then school is in session.

In a different, better world, “Get Hard” might have been an incisive yet raucous look across the racial, income, and criminal divide. Heck, forget that, it might have just been funny.

In this duller, lesser world, it’s a tired, fish-out-of-water story weighed down by predictably middle-school jokes. An excursion to a West Hollywood gay bar is painfully unfunny.

If there’s a saving grace, it’s found in Hart, whose firecracker energy should be harnessed to power the electric grid. There’s a scene in which, while showing James how to handle himself on the prison yard, he plays three distinct characters — one black, one Latino, and one black and gay. It’s a couple of minutes of unrivaled hilarity that the rest of the movie can’t match.

What’s worse, first-time feature director Etan Cohen (not to be confused with Ethan Coen of the Coen Brothers), working from a script he wrote with two others, doesn’t seem to try that hard. It’s as if he thought that just putting Hart and Ferrell on the same set would be enough. Sadly, it’s not.

Speaking of which, Ferrell is fine and, as usual, throws himself into the role with enthusiasm, but most of the material just isn’t worth the effort.

Some of the supporting players, especially a convincing turn from rapper T.I. as the head of an LA gang and John Mayer as John Mayer, provide some diversion from the dearth of real humor.

By the time “Get Hard” limps into its final act — turning from “My Fair Lady” with two dudes into generic comic-thriller with two dudes — it has totally lost whatever steam it had and squandered much of its comedic potential.

Since anyone who has seen the trailer has already seen many of the film’s best moments, making it through to the end does feel like something of a life sentence. And that truly is hard.