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.

• Run

      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 .