How to install Open JDK in Ubuntu

You can refer http://openjdk.java.net/ to know what is Open JDK. In this I will be installing Open jdk version 1.7.0_25

1. You can download your referred version from http://www.oracle.com/technetwork/java/javase/downloads/index.html
    
2. Once you download, uncompress the file using following command
   
   sudo tar -xvf jdk-7u25-<version>.tar.gz
   
   JDK 7 package is extracted into /jdk1.7.0_25 directory.
   
   
3. It is better to move the JDK 7 directory to /usr/lib via following commands
   

            sudo mkdir -p /usr/lib/jvm
            sudo mv jdk1.7.0_25/ /usr/lib/jvm/jdk1.7.0_25

4. Then run the following commands :
   

sudo update-alternatives --install “/usr/bin/java” “java” “/usr/lib/jvm/jdk1.7.0_25/bin/java” 1
sudo update-alternatives --install “/usr/bin/javac” “javac” “/usr/lib/jvm/jdk1.7.0_25/bin/javac” 1
sudo update-alternatives --install “/usr/bin/javaws” “javaws” “/usr/lib/jvm/jdk1.7.0_25/bin/javaws” 1

5. Then configure for the open jdk
   For Java :
   sudo update-alternatives --config java
   

This will output the following

There are 5 choices for the alternative java (providing /usr/bin/java).

Selection Path Priority Status

------------------------------------------------------------

0 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java 1061 auto mode

1 /opt/java/jdk1.7.0_25/bin/java 1 manual mode

2 /opt/java/jre1.7.0_25/bin/java 1 manual mode

3 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java 1061 manual mode

* 4 /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java 1051 manual mode

5 /usr/lib/jvm/jdk1.7.0_25/bin/java 1 manual mode

You have to Press enter to keep the current choice[*], or type selection number. In here I will be entering * since I need the 4th option.

For Javac :
sudo update-alternatives --config javac

This will output the following

There are 3 choices for the alternative javac (providing /usr/bin/javac).

Selection Path Priority Status

------------------------------------------------------------

0 /usr/lib/jvm/java-6-openjdk-amd64/bin/javac 1061 auto mode

1 /usr/lib/jvm/java-6-openjdk-amd64/bin/javac 1061 manual mode

* 2 /usr/lib/jvm/java-7-openjdk-amd64/bin/javac 1051 manual mode

3 /usr/lib/jvm/jdk1.7.0_25/bin/javac 1 manual mode

You have to Press enter to keep the current choice[*], or type selection number. In here I will be entering * since I need the 2nd option.

For Javaws :
sudo update-alternatives --config javaws

This will output the following

There are 3 choices for the alternative javaws (providing /usr/bin/javaws).

Selection Path Priority Status

------------------------------------------------------------

0 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/javaws 1061 auto mode

1 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/javaws 1061 manual mode

* 2 /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/javaws 1060 manual mode

3 /usr/lib/jvm/jdk1.7.0_25/bin/javaws 1 manual mode

You have to Press enter to keep the current choice[*], or type selection number. In here I will be entering * since I need the 2nd option.

6. Now you can check the java version
   java -version
   

This will output the following if the installation is successful :

java version "1.7.0_25"
OpenJDK Runtime Environment (IcedTea 2.3.10) (7u25-2.3.10-1ubuntu0.12.04.2)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)

7. Also you have to set JAVA_HOME in .bashrc.
   Run the following command and open the .bashrc and give the correct path.
   gedit ~/.bashrc
   Add the following to the end of the file.
   
   export JAVA_HOME=/usr/lib/jvm/java-1.7.0_25
   export PATH=$PATH:$JAVA_HOME/bin
8. Source the bash profile.
   source ~/.bashrc