How do I install Oracle Java JDK 7?

There is a similar question on how to install JRE 7.

Install the JDK

Download he 32bit or 64bit Linux "compressed binary file" - it has a ".tar.gz" file extension i.e. "[java-version]-i586.tar.gz" for 32bit and "[java-version]-x64.tar.gz" for 64bit
Uncompress it

tar -xvf jdk-7u2-linux-i586.tar.gz (32bit)

tar -xvf jdk-7u2-linux-x64.tar.gz (64bit)

JDK 7 package is extracted into ./jdk.1.7.0_02 directory. N.B. check carefully this folder name since Oracle seem to change this occasionally with each update.

Now move the JDK 7 directory to /usr/lib

sudo mkdir -p /usr/lib/jvm
sudo mv ./jdk.1.7.0_02 /usr/lib/jvm/jdk1.7.0

Now run

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.7.0/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.7.0/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.7.0/bin/javaws" 1

Correct the permissions of the executables:

sudo chmod a+x /usr/bin/java 
sudo chmod a+x /usr/bin/javac 
sudo chmod a+x /usr/bin/javaws

N.B. remember - Java JDK has many more executables that you can similarly install as above. java, javac, javaws are probably the most frequently required.

This answer lists the other executables available.

sudo update-alternatives --config java

You will see output similar one below - choose the number of jdk1.7.0 - for example 3 in this list:

$sudo update-alternatives --config java
There are 3 choices for the alternative java (providing /usr/bin/java).

Selection Path Priority Status
————————————————————
* 0 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 auto mode
1 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 manual mode
2 /usr/lib/jvm/java-6-sun/jre/bin/java 63 manual mode
3 /usr/lib/jvm/jdk1.7.0/jre/bin/java 3 manual mode

Press enter to keep the current choice[*], or type selection number: 3
update-alternatives: using /usr/lib/jvm/jdk1.7.0/jre/bin/java to provide /usr/bin/java (java) in manual mode.

Check the version of you new JDK 7 installation:

java -version

java version “1.7.0”
Java(TM) SE Runtime Environment (build 1.7.0-b147)
Java HotSpot(TM) Client VM (build 21.0-b17, mixed mode)

Repeat the above for:

sudo update-alternatives --config javac
sudo update-alternatives --config javaws

Enable mozilla firefox plugin:

32 bit:
ln -s /usr/lib/jvm/jdk1.7.0/jre/lib/i386/libnpjp2.so ~/.mozilla/plugins/

64 bit:
ln -s /usr/lib/jvm/jdk1.7.0/jre/lib/amd64/libnpjp2.so ~/.mozilla/plugins/

N.B. you can link the plugin (libnpjp2.so) to /usr/lib/firefox/plugins/ for a system wide installation

Depending on your configuration, you might need to update the apparmor profile for firefox (or other browsers) in /etc/apparmor.d/abstractions/ubuntu-browsers.d/java

# Replace the two lines:
#  /usr/lib/jvm/java-*-sun-1.*/jre/bin/java{,_vm} cx -> browser_java,
#  /usr/lib/jvm/java-*-sun-1.*/jre/lib/*/libnp*.so cx -> browser_java,
# with those (or adapt to your new jdk folder name)
/usr/lib/jvm/jdk*/jre/bin/java{,_vm} cx -> browser_java,
/usr/lib/jvm/jdk*/jre/lib/*/libnp*.so cx -> browser_java,

Then restart apparmor:

sudo /etc/init.d/apparmor restart

Confirm that the JRE has been successful by using the official oracle website.

For Java 6:

How do I install Oracle JDK 6?

If you're on a fresh installation of Ubuntu with no previous Java installations, this script automates the process outlined above if you don't want to type all that into a console. Remember, you still need to download Java from Oracle's website -- Oracle's links are not wget friendly.

Before using this make sure that this script is in the same directory as the .tar.gz file extension that you downloaded and there are no files that start with jdk-7 in the same folder -- if there are, please move them out of the folder temporarily. Remember to make the script executable, either by doing chmod +x <script's directory> or right clicking the document, pressing properties, going to the Permissions tab, and checking "Allow executing file as a program."

#!/bin/sh

tar -xvf jdk-7*
sudo mkdir /usr/lib/jvm
sudo mv ./jdk1.7* /usr/lib/jvm/jdk1.7.0
sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.7.0/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.7.0/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.7.0/bin/javaws" 1
sudo chmod a+x /usr/bin/java
sudo chmod a+x /usr/bin/javac
sudo chmod a+x /usr/bin/javaws

If you want to install the plugin for Firefox then add this to the end of the script

mkdir ~/.mozilla/plugins
ln -s /usr/lib/jvm/jdk1.7.0/jre/lib/amd64/libnpjp2.so ~/.mozilla/plugins/
sudo /etc/init.d/apparmor restart

Confirm if Java has been properly installed.

java -version

Confirm that the JRE Mozilla plugin has been successful by using the official oracle website.