If for some reasons the Java Open-JDK runtime environment doesn’t suit your needs, these are the necessary step to install the Oracle JDK.
First you need to download the proper package by clicking here

We’re going to download version 8 update 6 for ARM hard float, since current UDOO’S Ubuntu is the hard float version.

If Java 8 update 6 is no longer featured, you can find the download by using this previous releases link found on the main download page.

Once the download has finished, open the downloaded package by double-clicking on it. Before extracting it, we must set correct privileges into destination folder, which is /usr/lib/jvm

sudo chmod -R 777 /usr/lib/jvm

Now we can extract the files, so point the extraction to /usr/lib/jvm

tar xzvf .tar.gz -C /usr/lib/jvm/

Once done, we inform Ubuntu where Java installation resides

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.8.0_06/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.8.0_06/bin/javac" 1

And make it the default Java installation

sudo update-alternatives --set java /usr/lib/jvm/jdk1.8.0_06/bin/java
sudo update-alternatives --set javac /usr/lib/jvm/jdk1.8.0_06/bin/javac

Edit your /etc/profile file using:

sudo nano /etc/profile

if you don’t have nano installed

sudo apt-get install nano

Add the following entries to the bottom of the file:

JAVA_HOME=/usr/lib/jvm/jdk1.8.0_06
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JAVA_HOME
export PATH

Save your changes using CTRL + X

Now, reload system-wide path with

. /etc/profile

Let’s test our new Java installation

java –version

Response:

java version "1.8.0_06"
Java(TM) SE Runtime Environment (build 1.8.0_06-b18)
Java HotSpot(TM) Client VM (build 24.45-b08, mixed mode)

javac –version

Response:

javac 1.8.0_06

 

 

Done, you’ve succeeded in installing Java on UDOO!