LAS VEGAS  >> Floyd Mayweather Jr. turned himself in Friday in a Las Vegas courtroom to begin serving a three-month jail sentence for attacking his ex-girlfriend in September 2010 while two of their children watched.

The undefeated five-division champion said nothing as he stood in a gray sweatsuit and sneakers before a judge who credited him with fulfilling community service requirements she imposed in December, then watched as Mayweather was handcuffed and taken away.

Justice of the Peace Melissa Saragosa had allowed Mayweather to remain free long enough to headline a May 5 fight.

Mayweather pleaded guilty in December to reduced domestic battery charges in a hair-pulling, arm-twisting attack on the mother of three of his children. The plea deal avoided trial on felony charges that could have gotten Mayweather up to 34 years in prison if he was convicted.

“He’ll be all right,” Mayweather friend, rapper 50 Cent, told reporters outside the courthouse.

Las Vegas police say that as a high-profile inmate, Mayweather probably will serve most of his time away from other prisoners in a small solo cell.

Mayweather, who goes by the nickname “Money,” will have a cell about one-third the size of a small boxing ring. His stint in the high-rise Clark County Detention Center is expected to limit his ability to train for another fight.

At least for the first week, Mayweather will be segregated for his protection from the other 3,200 inmates in the downtown Las Vegas facility, police Officer Bill Cassell said this week.

Mayweather won’t have a TV in his cell, and Cassell said televisions in jail dining areas probably won’t carry the June 9 pay-per-view WBO welterweight fight between Mayweather rival Manny Pacquiao and Timothy Bradley at the MGM Grand Garden arena.

The judge sentenced Mayweather on Dec. 22, then later allowed him to remain free long enough to fight Miguel Cotto on May 5 in Las Vegas.

Mayweather was accompanied into the ring by entertainers Justin Bieber and 50 Cent before winning the Cinco de Mayo weekend bout and a guaranteed $32 million. Cotto was paid $8 million.

Saragosa said when she sentenced Mayweather that she was particularly troubled that he threatened and hit ex-girlfriend Josie Harris while their two sons watched. The boys were 10 and 8 at the time. The older boy ran out a back door to get a security guard in the gated community.

However, the judge accepted the deal that had Mayweather plead guilty to misdemeanor domestic battery and no contest to two harassment charges. Prosecutors dropped other charges.

Mayweather’s jail stay will be capped at 87 days, because the judge gave him credit for three days previously served. It could be reduced by several weeks for good behavior, Cassell said Thursday. Mayweather also was ordered to complete a yearlong domestic violence counseling program, 100 hours of community service and pay a $2,500 fine.

Harris and the three children now live in Southern California.

Mayweather will be housed in a standard administrative segregation cell no larger than 7-by-12 feet, with a bunk, stainless steel toilet and sink, a steel and wood desk with a permanently bolted stool and two small vertical windows with opaque safety glass.

The cell will be a far cry from Mayweather’s nearly 12,800-square-foot, two-story mansion on a cul de sac in an exclusive guarded community several miles south of the Las Vegas Strip. Mayweather’s home has two garages, five bedrooms, eight bathrooms, and a swimming pool and hot tub overlooking a golf course.

Mayweather could have about an hour a day out of his cell with access to an exercise yard, Cassell said. Depending on his behavior, the boxer could later get several hours a day for exercise with other inmates also being held in protective custody.

He’ll get a standard-issue blue jail jumpsuit with the letters CCDC and orange slippers. Mayweather will be able to deposit money into a jail account to purchase snacks, soap and personal hygiene items from the jail commissary.