403

I've installed a version of Java. How can we set the $JAVA_HOME environment variable correctly?

Improve this question

5 Answers 5

Reset to default
539

You can set your JAVA_HOME in /etc/profile as Petronilla Escarabajo suggests. But the preferred location for JAVA_HOME or any system variable is /etc/environment.

Open /etc/environment in any text editor like nano or gedit and add the following line:

JAVA_HOME="/usr/lib/jvm/open-jdk"

(java path could be different)

Use source to load the variables, by running this command:

source /etc/environment

Then check the variable, by running this command:

echo $JAVA_HOME

Update

Usually most linux systems source /etc/environment by default. If your system doesn't do that add the following line to ~/.bashrc (Thanks @pje)

source /etc/environment
Improve this answer
14
  • 2
    When i tried to run Android Studio (that has IntelliJ IDEA as a base), i had an error message very similar to @advocate's: "'tools.jar' seems to be not in Android Studio classpath." After fiddling a lot with JAVA_HOME without success, i decided to take a look at studio.sh, the shellscript that starts Android Studio. As a wild guess, i set JDK_HOME to the same value expected for JAVA_HOME, and voila! It installed without great problems. Commented Mar 7, 2015 at 23:20
  • 6
    For those doing software development, don't put your JAVA_HOME in /etc/environment unless you want to reboot everytime you switch JDK versions. Commented Sep 20, 2016 at 19:03
  • 3
    This is a temporary solution, as others pointed out. No one would want to run source every time they restart their bash. Commented Feb 19, 2017 at 21:49
  • 7
    As others have pointed out, this doesn't stick between terminal sessions. What I did to address this is just added the line source /etc/environment to the top of my bash config file ~/.bashrc so that it loads all my environment settings on startup. Working for me so far. Commented Mar 11, 2017 at 22:31
  • 2
    @sedulam I updated the answer Commented Apr 20, 2017 at 6:20
88

To set JAVA_HOME environment variable, do the following:

  1. Launch Terminal by pressing Ctrl+Alt+T on your keyboard.
  2. Enter the following command:
    $ gksudo gedit /etc/environment
  3. Depending on where you installed your Java, you will need to provide the full path. For this example, I installed Oracle JDK 7 in the /usr/lib/jvm/java-7-oracle directory.
    Scroll to the end of the file and enter the following:
    JAVA_HOME=/usr/lib/jvm/java-7-oracle
    export JAVA_HOME
  4. Save your file and exit gedit.
  5. Lastly, reload the system PATH with the following command:
    $ . /etc/environment

The above method will save you the hassle in having to run the commands every time you log in to your computer.

Improve this answer
6
  • 7
    How does . /etc/environment work? Commented Sep 13, 2016 at 13:36
  • 1
    Is the addition of the export command necessary in the /etc/environment ? Commented Nov 23, 2016 at 10:01
  • @pkaramol I've had to add export JAVA_HOME on 16.04LTS to make it load at startup. Commented Jan 20, 2017 at 6:20
  • 4
    @adeen-s You added export to a line in /etc/environment and it helped? That file contains variable definitions parsed as =-delimited name-value pairs; its contents are not executed as commands. (See man pam_env.) So unless you're separately treating the file as though it were a script (such as by passing /etc/environment to bash's ./source builtin), I wouldn't expect that to work. Commented Aug 17, 2017 at 16:02
  • 1
    > How does . /etc/environment work? -- . (dot) loads commands from a file askubuntu.com/a/232938/189965 Commented Sep 22, 2018 at 7:32
52

If you do not know the path and you only have openJDK installed, you can type update-alternatives --config java and you should find the path. To set the variable you can write JAVA_HOME=<PATH> followed by export JAVA_HOME. Notice there's no space when declaring the variable. To check if the variable is stored you simply type echo $JAVA_HOME to verify.

Improve this answer
5
  • 1
    This seems like it would be static. If I remove openjdk-7 and install openjdk-9, won't the JAVA_HOME then point to the wrong place? How can it be made dynamic? Commented Jul 20, 2016 at 18:49
  • 3
    By you manually changing it. Once again, YOU are the way it becomes dynamic.... Commented Sep 20, 2016 at 19:04
  • What @HDave means is that In certain cases, you may want JAVA_HOME to point to a specific java version, so making the update of JAVA_HOME dynamic may not be what you want. Commented Oct 9, 2016 at 15:31
  • i like this answer. I tested with echo and see my path. However, I am confused why I am still getting JAVA_HOME environment variable is not set when I run mvn -version Commented Apr 11, 2017 at 22:19
  • 4
    I wrote this answer back when I was more ignorant. Setting the variable as described will only affect your current terminal session, and will not be persisted. The correct way is to run update-alternatives --install <link> <name> <target> <priority> for example: update-alternatives --install /usr/bin/java java /usr/lib/jvm/default-runtime/bin/java 1 Commented May 14, 2017 at 12:26
4

This is the best option if you always want to use the latest one installed.
Nowadays (Ubuntu 23.10) you should probably have it installed through apt like:

sudo apt install default-jdk # or default-jre

In this case, you should find it at /usr/lib/jvm/default-java.
It's a symlink that points to whichever the current JVM is on the same folder.
So, just run this to add the environment as a separate file:

sudo nano /etc/environment.d/90java.conf

Add this line and save:

JAVA_HOME="/usr/lib/jvm/default-java"

Then reboot or login again, or source /etc/environment.d/90java.conf to load it on the current shell.

Improve this answer
1
  • Wasn't there for me. If you use zulu it's under /usr/lib/jvm/zulu17 Commented Jun 12, 2024 at 1:29
0

IMHO the best approach (which doesn't require any non-standard software to be installed) is to put the following near the end of your .bashrc:

jvm=$(update-alternatives --query java | grep '^Value:' | cut -f2 -d' ') ; export JAVA_HOME=${jvm%/*/*}

This should keep JAVA_HOME up to date even if the software gets updated (say to JDK 21 or 25); although you'll have to log out/in sessions for this to take effect.

Testing (after logging out/in the session):

echo $JAVA_HOME /usr/lib/jvm/java-17-openjdk-amd64 $JAVA_HOME/bin/java --version openjdk 17.0.15 2025-04-15 OpenJDK Runtime Environment (build 17.0.15+6-Ubuntu-0ubuntu120.04) OpenJDK 64-Bit Server VM (build 17.0.15+6-Ubuntu-0ubuntu120.04, mixed mode, sharing)

Explanation:

  • update-alternatives --query java: displays Ubuntu's available JVMs (more than one can be installed; only one is the default; this is indicated by the line that starts with Value: )
  • grep '^Value:' | cut -f2 -d' ': takes the output of the previous command and extracts the path of the default java executable (that launches the JVM).
  • export JAVA_HOME=${jvm%/*/*}: JAVA_HOME must point to the root of the JVM installation, not the java executable. The Bash parameter substitution ${jvm%/*/*} strips the last two components from the java executable's path returned by the previous command.
Improve this answer

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.