Setting a JAVA HOME Path in Ubuntu

Notes from reconfiguring JAVA_HOME while switching from OpenJDK 8 to 11

1. Install

sudo apt-get install openjdk-11-jdk

• This command also installs the openjdk-11-jre package which contains the Java runtime environment!

2. Check the version

chloe@chloe-XPS-15-9570 ~
$ java -version
openjdk version "11.0.8" 2020-07-14
OpenJDK Runtime Environment (build 11.0.8+10-post-Ubuntu-0ubuntu118.04.1)
OpenJDK 64-Bit Server VM (build 11.0.8+10-post-Ubuntu-0ubuntu118.04.1, mixed mode, sharing)

3. Find where JDK is installed

• You can find the installed JDKs by navigating to the /usr/lib/jvm/ path

  chloe@chloe-XPS-15-9570 ~
  $ cd /usr/lib/jvm/
  
  chloe@chloe-XPS-15-9570 /usr/lib/jvm
  $ ls
  default-java     java-11-openjdk-amd64     java-8-openjdk-amd64
  java-1.11.0-openjdk-amd64  java-1.8.0-openjdk-amd64  openjdk-11
  

4. Set environment variable

Open /etc/environment with vim

sudo vi /etc/environment

Add the following environment variable

JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
export JAVA_HOME

Apply the modified values immediately using the source command

source /etc/environment

5. Check the environment variable

5-1. Check the configured environment variable using the echo command

chloe@chloe-XPS-15-9570 /usr/lib/jvm
$ echo $JAVA_HOME
/usr/lib/jvm/java-11-openjdk-amd64

5-2. Check using the printenv command

chloe@chloe-XPS-15-9570 /usr/lib/jvm
$ printenv | grep "java"
JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64

• Using grep allows you to search for a specific string!

  • Here we are searching for "java"!

Done!

+

When you want to switch between alternatives and build with a specific version

chloe@chloe-XPS-15-9570 ~
$ sudo update-alternatives --config java
[sudo] password for chloe:
There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

Press <enter> to keep the current choice[*], or type selection number:

• You can change to the desired version by entering its number