Pi Jessie Static IP

/etc/network/interfaces

iface wlan0 inet static
static address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.1

/etc/dhcp.conf

interface wlan0
static ip_address=192.168.1.2/24
static routers=192.168.1.1
static domain_name_servers=192.168.1.1 8.8.8.8 8.8.4.4