N.J. Stat. Ann. § 40A:9-116

Except as hereinafter provided, in all counties the sheriff may appoint not more than three undersheriffs. In counties in which the sheriff assumes the custody, keeping and charge of the county jail or jails and all prisoners therein, as provided by R.S.30:8-17, the sheriff may appoint one additional undersheriff. All such undersheriffs shall hold office during the pleasure of the sheriff making the appointment, or his successor. The undersheriffs shall be included in the unclassified service of the civil service.