Yep, you suggested run this example, how to build it?
Have compilation errors
in my case module located here
[21:25:17] openhabian@openHABianPi:~/pi4j/pi4j/pi4j-example/src/main/java$ sudo find / -iname MCP23017GpioProvider*
/home/openhabian/pi4j/pi4j/pi4j-gpio-extension/src/main/java/com/pi4j/gpio/extension/mcp/MCP23017GpioProvider.java