Good things to consider when using Java with your RPi.

[Marcus]

Install Oracle's JDK. I usually do this via synaptic.

Next don't forget to switch to the Oracle JDK:
sudo update-java-alternatives -s jdk-7-oracle-armhf

Next install Pi4J. If on Raspbian, follow the Raspbian instructions:
http://pi4j.com/install.html

For Dallas 1-wire support and i2c you probably want your /etc/modules to look like this:
snd-bcm2835
i2c-bcm2708
i2c-dev
w1-gpio
w1-therm

[Marcus]

Or interactively:
sudo update-alternatives --config java
sudo update-alternatives --config javac

[Marcus]

P4 on the PI:

Download ARMHF version. chmod +x. Copy to /usr/local/bin. Create .p4config with all settings. export P4CONFIG=/home/pi/.p4config in .bashrc.