Follow this guide to test JIRA performance:
https://github.com/atlassian/jira-performance-tests/blob/master/docs/tests/ON_PREMISE.md
Installed JAVA by:
$ sudo yum install java-11-openjdk-devel
Use this way got installed JAVA path:
$ update-alternatives --config java
java-11-openjdk.x86_64 (/usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64/bin/java)
Set /usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64/bin/java to ~/.bash_profile as env variable:
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64/bin/java
Source file:
$ source ~/.bash_profile
Check JAVA_HOME:
$ echo $JAVA_HOME
/usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64/bin/java
From JIRA test path run test command:
$ cd jira-performance-tests/examples/btf-test
$ ./mvnw verify
Got error:
Error: JAVA_HOME is not defined correctly.
We cannot execute /usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64/bin/java/bin/java
Why?
Usually JAVA_HOME is given without /bin/java.
I suggest changing the JAVA_HOME to /usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64.
add JAVA_HOME to the classpath
export PATH=$PATH:$JAVA_HOME/bin
Hey you can do something like this to export the Java_Home
export
JAVA_HOME="/usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64/"
export PATH=$PATH:$JAVA_HOME/bin
You should setup JAVA_HOME environment variable to:
/usr/lib/jvm/java-11-openjdk-11.0.5.10-0.el7_7.x86_64/bin/java/bin
To set JAVA_HOME, do one of the following:
For Korn and bash shells, run the following commands:
export JAVA_HOME=jdk-install-dir
export PATH=$JAVA_HOME/bin:$PATH
For the bourne shell, run the following commands:
JAVA_HOME=jdk-install-dir
export JAVA_HOME
PATH=$JAVA_HOME/bin:$PATH
export PATH
For the C shell, run the following commands:
setenv JAVA_HOME jdk-install-dir
setenv PATH $JAVA_HOME/bin:$PATH
export PATH=$JAVA_HOME/bin:$PATH
For more info have a look at documentation
I am using ubuntu 14.0.4... JAVA_HOME is always /usr/lib/jvm/java-7-oracle even though i uninstalled java...
I manually set /usr/lib/jvm/jdk1.8.0_71 in etc/environment. But $echo JAVA_HOME shows /usr/lib/jvm/java-7-oracle.
How to resolve this issue and how to use my jdk1.8.0_71 in JAVA_HOME.
Try edit ~/.profile. Add line at bottom:
JAVA_HOME="/usr/lib/jvm/jdk1.8.0_71"
After editing, close console (terminal) window and open new. Test with echo JAVA_HOME.
from terminal:
vi ~/.bash_profile
than change:
export JAVA_HOME= path_to_java_here
than:
source ~/.bash_profile
verify with:
echo $JAVA_HOME
How to get the java home dir?
When doing this
echo $JAVA_HOME
Nothing is returned
You need to set the $JAVA_HOME variable
In my case while setting up Maven, I had to set it up to where JDK is installed.
First find out where JAVA is installed:
$ whereis java
java: /usr/bin/java /usr/share/java /usr/share/man/man1/java.1.gz
Now dig deeper-
$ ls -l /usr/bin/java
lrwxrwxrwx 1 root root 46 Aug 25 2016 /etc/alternatives/java -> /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
Dig deeper:
$ ls -l /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
-rwxr-xr-x 1 root root 6464 Mar 14 18:28 /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
As it is not being referenced to any other directory, we'll use this.
Open /etc/environment using nano
$ sudo nano /etc/environment
Append the following lines
JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-amd64
export JAVA_HOME
Reload PATH using $ . /etc/environment
Now,
$ echo $JAVA_HOME
Here is your output:
/usr/lib/jvm/java-1.8.0-openjdk-amd64
Sources I referred to:
https://askubuntu.com/a/175519
https://stackoverflow.com/a/23427862/6297483
$JAVA_HOME is a global variable that you typically must set yourself.
In certain (most?) platforms, installing Java will not set your JAVA_HOME variable.
The advantage here is that you can have multiple Java versions co-existing within one system.
Since you're running on *nix system, you can do that in your own logon scripts, such as ~/.bashrc or ~/.bash_profile, etc.
Open your terminal, and open your .bash_profile file by executing:
nano ~/.bash_profile
(If it is the first time, it should be empty)
2. Ad an echo message just to see a greeting message by pasting
echo "Hello, Your Bash Profile Is Running…"
Type: ctrl + x to exit from nano
Type: Y to save change and press enter
In order to get the message to appear every time we open a terminal execute:
source ~/.bash_profile
In the file ~/.bash_profile, set the $JAVA_HOME environment variable by adding the
following to the end of the file:
export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk13.jdk/Contents/Home"
export PATH="$JAVA_HOME/bin:$PATH"
Type: ctrl + x to exit from nano
Type: Y to save change and press enter
Close and reopen your terminal to update the environment variables.
Verify JAVA_HOME by executing echo $JAVA_HOME.
Source: https://www.youtube.com/watch?v=0gceUrMnjzo
If you are using latest versions of OS, then you cannot use ~/.bash_profile to export your environment variable since bash shell is deprecated in the latest version of OS.
This answer may give you the exact solution:https://stackoverflow.com/a/62192114/3962688
If the terminal is zsh and not bash then we need to set JAVA_HOME in either of these files ~/.zshenv or ~/.zshrc more details about zsh terminal here
steps:
run this command in the terminal open ~/.zshrc
in the zshrc file append java_home path (refer below two lines)
export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk-x.x.x.jdk/Contents/Home"
export PATH="$JAVA_HOME/bin:$PATH"}
re-launch zsh terminal
In the zsh terminal run this command echo $JAVA_HOME
What solved to me, using Ubuntu 18, was removing java from /etc/profile
So, export JAVA_HOME=/usr/bin
set it first?
export JAVA_HOME=/usr/bin/java
See more here:
How to set JAVA_HOME in Linux for all users
I tried running ./gradlew from an Android project directory, but I get an error of:
ERROR: JAVA_HOME is set to an invalid directory:
/Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk/Contents/Home
Please set the JAVA_HOME variable in your environment to match the
location of your Java installation.
Things I've tried:
Navigated to /Library/Java/JavaVirtualMachines. jdk1.8.0_11.jdk exists, but so does jdk1.7.0_79.jdk
which java prints out /usr/bin/java
printenv prints
...
JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk/Contents/Home
JDK_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk/Contents/Home
...
javac -version prints javac 1.8.0_11
which javac prints /usr/bin/javac
Check if /usr/libexec/java_home exists. If it does then try running
export JAVA_HOME=`/usr/libexec/java_home`
and rerunning your gradlew build. If it works then make it permanent with
echo export "JAVA_HOME=\$(/usr/libexec/java_home)" >> ~/.bash_profile
For me, I got that error no matter what I tried. Deleting the JAVA_HOME var worked for me.
If you see this message in 2021 after upgrading to Android Studio Arctic Fox (2020.3.1) Stable, then the following answer should help to get yourself unblocked.
Open the "Project Structure" window from the "File" menu and you can see that the JDK location is now moved to the Gradle settings.
Now, click on the Gradle Settings link and you can see another window in which the current JDK location is specified.
Now you should edit your ~/.bashrc OR ~/.zshrc to update the value of JAVA_HOME env variable.
That's it!
Now run the source ~/.bashrc OR source ~/.zshrc command or restart your terminal and enjoy running the ./gradlew command in your project.
Cheers!
I have added the following to my .bash_profile to help sort out issues such as this one. This has the added benefit of being able to run setjdk {version} and switch java versions on the fly.
function setjdk() {
if [ $# -ne 0 ]; then
removeFromPath '/System/Library/Frameworks/JavaVM.framework/Home/bin'
if [ -n "${JAVA_HOME+x}" ]; then
removeFromPath $JAVA_HOME
fi
export JAVA_HOME=`/usr/libexec/java_home -v $#`
export PATH=$JAVA_HOME/bin:$PATH
fi
}
function removeFromPath() {
export PATH=$(echo $PATH | sed -E -e "s;:$1;;" -e "s;$1:?;;")
}
#Default JDK to Java 8
setjdk 1.8
Try this instead form Mac os
export JAVA_HOME="/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home"
In macOS, the JDK installation path is/Library/Java/JavaVirtualMachines/jdk-10.jdk/Contents/Home. See the official documentation.
If anyone comes here using fish, adding the following line to ~/.config/fish/config.fish solves the problem for me.
set JAVA_HOME (/usr/libexec/java_home -v (java --version | awk 'NR==1{print $2}'))
I just installed JDK in Ubuntu with sudo apt-get install openjdk-6-jdk command,
after the installation where's the Java bin directory located? And how can I set the environment path for that directory? I have little experience with Ubuntu, can anyone give some advice or suggest any good website for reference?
set environment variables as follows
Edit the system Path file /etc/profile
sudo gedit /etc/profile
Add following lines in end
JAVA_HOME=/usr/lib/jvm/jdk1.7.0
PATH=$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...
Java is typically installed in /usr/java
locate the version you have and then do the following:
Assuming you are using bash (if you are just starting off, i recommend bash over other shells) you can simply type in bash to start it.
Edit your ~/.bashrc file and add the paths as follows:
for eg. vi ~/.bashrc
insert following lines:
export JAVA_HOME=/usr/java/<your version of java>
export PATH=${PATH}:${JAVA_HOME}/bin
after you save the changes, exit and restart your bash or just type in bash to start a new shell
Type in export to ensure paths are right.
Type in java -version to ensure Java is accessible.
Ubuntu installs openjdk6 to /usr/lib/jvm/java-6-openjdk path. So you will have the bin in /usr/lib/jvm/java-6-openjdk/bin. Usually the classpath is automatically set for the java & related executables.
To Set JAVA_HOME / PATH for a single user, Login to your account and open .bash_profile file
$ vi ~/.bash_profile
Set JAVA_HOME as follows using syntax export JAVA_HOME=<path-to-java>. If your path is set to /usr/java/jdk1.5.0_07/bin/java, set it as follows:
export JAVA_HOME=/usr/java/jdk1.5.0_07/bin/java
Set PATH as follows:
export PATH=$PATH:/usr/java/jdk1.5.0_07/bin
Feel free to replace /usr/java/jdk1.5.0_07 as per your setup. Save and close the file. Just logout and login back to see new changes. Alternatively, type the following command to activate the new path settings immediately:
$ source ~/.bash_profile
OR
$ . ~/.bash_profile
Verify new settings:
$ echo $JAVA_HOME
$ echo $PATH
Tip: Use the following command to find out exact path to which java executable under UNIX / Linux:
$ which java
Please note that the file ~/.bashrc is similar, with the exception that ~/.bash_profile runs only for Bash login shells and .bashrc runs for every new Bash shell.
To Set JAVA_HOME / PATH for all user, You need to setup global config in /etc/profile OR /etc/bash.bashrc file for all users:
# vi /etc/profile
Next setup PATH / JAVA_PATH variables as follows:
export PATH=$PATH:/usr/java/jdk1.5.0_07/bin
export PATH=$PATH:/usr/java/jdk1.5.0_07/bin
Save and close the file. Once again you need to type the following command to activate the path settings immediately:
# source /etc/profile
OR
# . /etc/profile
You need to set the $JAVA_HOME variable.
In my case while setting up Maven, I had to set it up to where JDK is installed.
First find out where JAVA is installed:
$ whereis java
java: /usr/bin/java /usr/share/java /usr/share/man/man1/java.1.gz
Now dig deeper:
$ ls -l /usr/bin/java
lrwxrwxrwx 1 root root 46 Aug 25 2018 /etc/alternatives/java -> /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
Dig deeper:
$ ls -l /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
-rwxr-xr-x 1 root root 6464 Mar 14 18:28 /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
As it is not being referenced to any other directory, we'll use this.
Open /etc/environment using nano:
$ sudo nano /etc/environment
Append the following lines
JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-amd64
export JAVA_HOME
Reload PATH using:
$. /etc/environment
Now:
$ echo $JAVA_HOME
Here is your output:
/usr/lib/jvm/java-1.8.0-openjdk-amd64
Sources I referred to:
https://askubuntu.com/a/175519
https://stackoverflow.com/a/23427862/6297483
if you have intalled only openJDK, the you should update your links, because you can have some OpenJDK intallation.
sudo update-alternatives --config java
after this
$gedit ~/.bashrc
add the following line in the file
JAVA_HOME=/usr/lib/jvm/YOUR_JAVA_VERSION
export PATH=$PATH:$JAVA_HOME/bin
export JAVA_HOME
you can get you java version with
java -version
Open terminal (Ctrl+Alt+t)
Type
sudo gedit .bashrc
Enter password of ubuntu user
Go to last line of the file
Type below code in new line
export JAVA_HOME=enter_java_path_here
export PATH=$JAVA_HOME/bin:$PATH
eg: export JAVA_HOME=/home/pranav/jdk1.8.0_131
export PATH=$JAVA_HOME/bin:$PATH
Save the file
Type
source ~/.bashrc
in terminal
Done
To set up system wide scope you need to use the
/etc/environment file sudo gedit /etc/environment
is the location where you can define any environment variable. It can be visible in the whole system scope. After variable is defined system need to be restarted.
EXAMPLE :
sudo gedit /etc/environment
Add like following :
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"
JAVA_HOME="/opt/jdk1.6.0_45/"
Here is the site you can find more : http://peesquare.com/blogs/environment-variable-setup-on-ubuntu/
How to install java packages:
Install desired java version / versions using official ubuntu packages, which are managed using alternatives:
sudo apt install -y openjdk-8-jdk
or/and other version:
sudo apt install -y openjdk-11-jdk
Above answers are correct only when you have only one version for all software on your machine, and you can skip using update-alternatives. So one can quickly hardcode it in .bashrc or some other place:
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-amd64
but it's not healthy, as later on you may change the version.
Correct way to set JAVA_HOME (and optionally JAVA_SDK, JAVA_JRE )
The correct way (and mandatory when you have more than one), is to detect what update-alternative is pointing to, and always use update-alternatives to switch active version.
Here are the suggestions for both: only specific unix account or for all accounts (machine level).
1. for a specific unix account only:
Use this if you don't have permissions to do it at machine level.
cat <<'EOF' >>~/.bashrc
export JAVA_HOME=$(update-alternatives --query java | grep Value | cut -d" " -f2 | sed 's!\(\/.*\)jre\(.*\)!\1!g')
export JDK_HOME=${JAVA_HOME}
export JRE_HOME=${JDK_HOME}/jre/
EOF
2. To do it at machine level, and for all bourne shells, you need 2 steps:
2.a
cat <<'EOF' | sudo tee /etc/profile.d/java_home_env.sh >/dev/null
export JAVA_HOME=$(update-alternatives --query java | grep Value | cut -d" " -f2 | sed 's!\(\/.*\)jre\(.*\)!\1!g')
export JDK_HOME=${JAVA_HOME}
export JRE_HOME=${JDK_HOME}/jre/
EOF
As your shell might not be set as interactive by default, you may want to do this also:
2.b
cat <<'EOF' | sudo tee -a /etc/bash.bashrc >/dev/null
if [ -d /etc/profile.d ]; then
for i in /etc/profile.d/*.sh; do
if [ -r $i ]; then
. $i
fi
done
unset i
fi
EOF
PS: There should be no need to update the $PATH, as update-alternatives takes care of the link to /usr/bin/.
More on: https://manpages.ubuntu.com/manpages/trusty/man8/update-alternatives.8.html
It should put java in your path, probably in /usr/bin/java. The easiest way to find it is to open a term and type which java.
Create/Open ~/.bashrc file $vim ~/.bashrc
Add JAVA_HOME and PATH as referring to your JDK path
export JAVA_HOME=/usr/java/<your version of java>
export PATH=${PATH}:${JAVA_HOME}/bin
Save file
Now type java -version it should display what you set in .bashrc file.
This will persist over sessions as well.
Example :
Update bashrc file to add JAVA_HOME
sudo nano ~/.bashrc
Add JAVA_HOME to bashrc file.
export JAVA_HOME=/usr/java/<your version of java>
export PATH=${PATH}:${JAVA_HOME}/bin
Ensure Java is accessible
java -version
In Case of Manual installation of JDK, If you got an error as shown below
Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object
Execute the following command in your JAVA_HOME/lib directory:
unpack200 -r -v -l "" tools.pack tools.jar
Execute the following commands in your JAVA_HOME/jre/lib
../../bin/unpack200 rt.pack rt.jar
../../bin/unpack200 jsse.pack jsse.rar
../../bin/unpack200 charsets.pack charsets.jar
Ensure Java is accessible
java -version
I have a Linux Lite 3.8 (It bases on Ubuntu 16.04 LTS) and a path change in the following file (with root privileges) with restart has helped.
/etc/profile.d/jdk.sh
Step1:
sudo gedit ~/.bash_profile
Step2:
JAVA_HOME=/home/user/tool/jdk-8u201-linux-x64/jdk1.8.0_201
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JAVA_HOME
export JRE_HOME
export PATH
Step3:
source ~/.bash_profile
Let me simplify:
download JDK from Oracle Website : Link
Extract it
Create a folder (jvm) in /usr/lib/ i.e /usr/lib/jvm
move the extracted folder from the jdk to /usr/lib/jvm/
*Note : use terminal, sudo, mv command i.e. sudo mv
Create a .sh file at /etc/profile.d/ eg: /etc/profile.d/myenvvar.sh
In the .sh file type
export JAVA_HOME=/usr/lib/jvm/jdk1.7.0
export PATH=$PATH:$JAVA_HOME/bin
*Note : use terminal, gedit and sudo eg: sudo gedit myenvvar.sh
Turn Off the Computer, after all these steps and Restart it
Open Terminal , and type
java -version
Check the output , then type
echo $JAVA_HOME
Once I've installed the openjdk version of the Java Development Kit on an Ubuntu machine, I use this procedure to create a JAVA_HOME environment variable that doesn't need to be changed after every version upgrade of the openjdk installation.
Firstly, I issue a command to discover the directory in which the java executables are located for this java installation.
echo $(readlink -e `which java` | xargs -0 dirname)
If I'm happy with the output from that, everything else can be derived from it.
Configuring the JAVA_HOME and PATH environment variables
Rather than adding more and more configurations to the ~/.bashrc file I've found it a cleaner practice to create a separate small file that ~/.bashrc can "include" when it runs.
Let's call that file ~/.java_env_vars (but you could name it whatever you wish).
Add an "include condition" to the ~/.bashrc file
Open ~/.bashrc in any text editor and these lines to the end of the file:
# include the java environment configuration file here (if it exists)
if [ -f "$HOME/.java_env_vars" ]; then
. $HOME/.java_env_vars
fi
Create the Java environment variable configuration file
Open any text editor, create the Java environment configuration file ~/.java_env_vars and add this content to it:
#1. set a java_bin variable to the directory containing the actual Java executables.
java_bin=$(readlink -e `which java` | xargs -0 dirname)
#2. append "$java_bin" to the PATH environment variable
export PATH=$PATH:"$java_bin"
#3. assign the directory of the current Java installation to the JAVA_HOME environment variable.
export JAVA_HOME=$(dirname "$java_bin")
NOTE: exporting the PATH and JAVA_HOME variables just ensures that they're always available wherever they're needed.
Source your ~/.bashrc file (so that the changes you made to it are reflected) using the following command:
source ~/.bashrc
Test the Java environment variable configuration
Open a new terminal console, and test the new Java environment variables by issuing this command:
echo "$PATH" && echo "$JAVA_HOME"
Output should be two lines, something like this:
/home/user/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/lib/jvm/java-11-openjdk-amd64/bin
/usr/lib/jvm/java-11-openjdk-amd64
All you have to do now is to set the “JAVA_HOME” and “PATH” environment variables and then you are done. Enter the following commands to set your environment variables. Make sure that your environment variables point to a valid installation of JDK on your machine. For Ubuntu 18.04, the path is /usr/lib/jvm/java-8-openjdk-amd64/
export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64
To check whether your JAVA_HOME path has been successfully saved, enter the following command to check.
echo $JAVA_HOME
Open file /etc/environment with a text editor
Add the line JAVA_HOME="[path to your java]"
Save and close then run source /etc/environment
Set java version from the list of installed. For see the list of the installed version run following command:
update-java-alternatives --list
Then set your java version according to the following command:
sudo update-java-alternatives --set /usr/lib/jvm/java-1.8.0-openjdk-amd64
open jdk once installed resides generally in your /usr/lib/java-6-openjdk
As usual you would need to set the JAVA_HOME, classpath and Path.
In ubuntu 11.04 there is a environment file available in /etc where you need to set all the three paths. And then you would need to restart your system for the changes to take effect..
Here is a site to help you around
http://aliolci.blogspot.com/2011/05/ubuntu-1104-set-new-environment.html
Once JDK installed set the JAVA_HOME in environment
sudo nano /etc/environment and add the line JAVA_HOME="/usr/lib/jvm/jdk-11.0.1/"
Add the configuration in .bashrc
sudo nano ~/.bashrc and add following lines
JAVA_HOME=/usr/lib/jvm/jdk-11.0.11/
PATH=$JAVA_HOME/bin:$PATH
refresh the new configuration with source ~/.bashrc
enter the command java -version and you can see the version installed on your machine
You can install the default Ubuntu(17.10) java from apt:
sudo apt install openjdk-8-jdk-headless
And it will set the PATH for you, if instead you need to install specific version of Java you can follow this YouTube
I installed java 11 in my Ubuntu 20.04. Setting up a JAVA_HOME for the same.
enter the this command to find out your ubuntu version --
swapnil#swapnil-vm:~$ lsb_release -d
Description: Ubuntu 20.04.3 LTS
enter this command to find out the location of your jvm --
swapnil#swapnil-vm:~$ whereis jvm
jvm: /usr/lib/jvm
open .bashrc in any editor of your choice --
nano .bashrc
add the following lines --
## setting JAVA_HOME
JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
export JAVA_HOME
PATH=$PATH:$JAVA_HOME/bin
export PATH
now you are good to go!!
open a new terminal and enter the command --
ehco $JAVA_HOME
Use the following lines to set the path variables in the /etc/environment
echo export JAVA_HOME=/path/to/java | sudo tee -a /etc/environment
echo export JRE_HOME=/path/to/jre | sudo tee -a /etc/environment
It should work.
Note:
You should reboot the system for changes to take effect.
Installation of Oracle Java:
Download the tarball (.tar file) from Oracle website
unzip it by sudo tar -xvpzf fileName -C /installation_folder_name
change the files permission and ownership
add the following two lines in /etc/profile
export JAVA_HOME=/home/abu/Java/jdk1.8.0_45/
export PATH=$JAVA_HOME/bin:$PATH
restart the machine and check by java -version and javac -version
First, check whether env var exists or not
echo $JAVA_HOME
if an env var exists with that name then the above command will return the env var Path. if it's return nothing then copy the env path first then execute below command. such as my java env path is /usr/lib/jvm/java-11-openjdk-amd64
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64