public WakeOnLan withMACAddress(String macStr) {
        if (macStr == null) throw new NullPointerException("MAC Cannot be null");
        this.macStr = macStr;
        return this;
    }
Set the mac address of the device to wake

@param macStr - The MAC address of the device to be woken (Required)
@return this object to allow chaining
library/src/main/java/com/stealthcopter/networktools/WakeOnLan.java