How to Set Oracle's Java as the Default Java in Ubuntu

How to set Oracle's Java as the default Java in Ubuntu?

I put the line:

export JAVA_HOME=/usr/lib/jvm/java-7-oracle

in my ~/.bashrc file.

/usr/lib/jvm/java7-oracle should be a symbolic link pointing to /usr/lib/jvm/java-7-oracle-[version number here].

The reason it's a symbolic link is that in case there's a new version of the JVM, you don't need to update your .bashrc file, it should automatically point to the new version.

If you want to set JAVA_HOME environment variables globally and at system level means use should set in /etc/environment file.

Ubuntu - Default Java, Oracle JDK not detected as installed

This was solved after setting the kava alternative

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/jdk/jdk1.8.0_144/bin/java" 1

sudo update-alternatives --install "/usr/bin/javac" "javac" "/opt/jdk/jdk1.8.0_144/bin/javac" 1

sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/opt/jdk/jdk1.8.0_144/bin/javaws" 1

It still install the default jdk when installing maven. But uses oracle jdk when building.

Thanks for the wikihow page : https://www.wikihow.com/Install-Oracle-Java-JDK-on-Ubuntu-Linux

How to set Java environment path in Ubuntu

set environment variables as follows

Edit the system Path file /etc/profile

sudo gedit /etc/profile

Add following lines in end

JAVA_HOME=/usr/lib/jvm/jdk1.7.0
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JAVA_HOME
export JRE_HOME
export PATH

Then Log out and Log in ubuntu for setting up the paths...

Replace openjdk with oracle-jdk on Ubuntu

You can completely remove the OpenJDK and fresh Install Oracle Java JDK by following these steps:

1. Remove OpenJDK completely by this command:

   sudo apt-get purge openjdk-\*
   

2. Download the Oracle Java JDK here.

   Note: download appropriate file, for example if your system is x64 Ubuntu (i.e, Debian) the download file is named like this: jdk-8u51-linux-x64.tar.gz

   To find which version is your OS, check here

3. Create a folder named java in /usr/local/by this command:

   sudo mkdir -p /usr/local/java
   

4. Copy the Downloaded file in the directory /usr/local/java. To do this, cd into directory where downloaded file is located and use this command for copying that file to /usr/local/java/:

   sudo cp -r jdk-8u51-linux-x64.tar.gz /usr/local/java/
   

5. CD into /usr/local/java/ directory and extract that copied file by using this command:

   sudo tar xvzf jdk-8u51-linux-x64.tar.gz
   

6. After extraction you must see a folder named jdk1.8.0_51.

7. Update PATH file by opening /etc/profile file by the command sudo nano /etc/profile and paste the following at the end of the file:

   JAVA_HOME=/usr/local/java/jdk1.8.0_51
   PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
   export JAVA_HOME
   export PATH
   

8. Save and exit.

9. Tell the system that the new Oracle Java version is available by the following commands:

   sudo update-alternatives --install "/usr/bin/java" "java" "/usr/local/java/jdk1.8.0_51/bin/java" 1
   sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/local/java/jdk1.8.0_51/bin/javac" 1
   sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jdk1.8.0_51/bin/javaws" 1
   

10. Make Oracle Java JDK as default by this following commands:

    sudo update-alternatives --set java /usr/local/java/jdk1.8.0_51/bin/java
    sudo update-alternatives --set javac /usr/local/java/jdk1.8.0_51/bin/javac
    sudo update-alternatives --set javaws /usr/local/java/jdk1.8.0_51/bin/javaws
    

11. Reload sytem wide PATH /etc/profile by this command:

    source /etc/profile
    

12. Reboot your system.

13. Check Java JDK version by java -version command . If installation is succesful, it will display like the following:

    java version "1.8.0_51"
    Java(TM) SE Runtime Environment (build 1.8.0_51-xxx)
    Java HotSpot(TM) Server VM (build 25.51-xxx, mixed mode)
    

That's it!

Note: We Assumed that the downloaded file is named jdk-8u51-linux-x64.tar.gz and used this name in all the commands used in steps 2, 4 and 5. It may depends on the type of O.S, processor type (i.e., 32bit or 64bit)

Where is Java path set by default?

Finally this is what worked for me, Thank you all for coming out so quickly for help. Unfortunately I can not verify the solution as I have already got it set , and even if I delete my setting and try solution mentioned above , because in the process I have changed many environment variables I can never be sure if this is what actually solved it ..
Sorry about that

http://www.webupd8.org/2012/01/install-oracle-java-jdk-7-in-ubuntu-via.html

How to install the JDK on Ubuntu Linux

Referring to Ask Ubuntu question How to set JAVA_HOME for OpenJDK?,

How to install Open JDK (Java developement kit) in Ubuntu (Linux)?

1. Open Terminal from Application Dash or press Ctrl+Alt+T

2. Update repository:

   sudo add-apt-repository ppa:openjdk-r/ppa  # only Ubuntu 17.4 and earlier
   sudo apt update
   

3. Optional: To search available distributions of openjdk, use the following command:

   apt search openjdk
   

4. Install the appropriate version with the following command:

   sudo apt install openjdk-8-jdk
   sudo apt install openjdk-8-source #this is optional, the jdk source code
   

5. For JAVA_HOME (Environment Variable) type command as shown below, in "Terminal" using your installation path...

   export JAVA_HOME=/usr/lib/jvm/java-8-openjdk
   

   (Note: /usr/lib/jvm/java-8-openjdk is symbolically used here just for demostration. You should use your path as per your installation.)

6. For PATH (Environment Variable) type command as shown below, in Terminal:

   export PATH=$PATH:$JAVA_HOME/bin

7. To check your installation:

   java -version

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