Pi4J uses an abstract pin numbering scheme to help insulate software from hardware changes.
P14J implements the same pin number scheme as the Wiring Pi project. More information about the WiringPi pin number scheme can be found here: http://wiringpi.com/pins/
Pi4J provides a RaspiPin enumeration that is used to manage the accessible GPIO pins.
The Raspberry Pi Zero board contains a single 40-pin expansion header labeled as 'J8' providing access to 28 GPIO pins.
(Pins 1, 2, 39 & 40 are also labeled below.)
The diagram below illustrates the GPIO pinout using the Pi4J/WiringPi GPIO numbering scheme.