OS: UBUNTU 18.04

I had installed Oracle Java 8 earlier. But decided to switch to open JDK 11. it's successfully installed.java -version
openjdk version "11.0.2" 2019-01-15 OpenJDK Runtime Environment (build 11.0.2+9-Ubuntu-3ubuntu118.04.3) OpenJDK 64-Bit Server VM (build 11.0.2+9-Ubuntu-3ubuntu118.04.3, mixed mode, sharing)

Then I set the JAVA_HOMEsudo nano /etc/environment File changes: PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/$ JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/"

Then executed: source /etc/environment

echo $JAVA_HOME
/usr/lib/jvm/java-11-openjdk-amd64/

But the moment I exit the terminal and then launch the terminal again:I get this output:

▶ echo $JAVA_HOME /usr/lib/jvm/java-8-oracle

which you can see is not what is expected. Please help me out

3 Answers

To Answer the question

The answers and some comments focus on how to set JAVA_HOME to version 11 but the question is partly about "where is version 8 being set?". To answer that see:

• `grep`ing all files for a string takes a long time

Use this command:

$ sudo grep -rnw --exclude-dir={boot,dev,lib,media,mnt,proc,root,run,sys,/tmp,tmpfs,var} '/' -e '/usr/lib/jvm/java-8-oracle' | grep JAVA_HOME
/etc/profile.d/jdk.sh:4:export JAVA_HOME=/usr/lib/jvm/java-8-oracle
/etc/profile.d/jdk.csh:4:setenv JAVA_HOME /usr/lib/jvm/java-8-oracle
/home/rick/.gradle/daemon/4.6/daemon-14831.out.log:53:20:45:23.553 [DEBUG] (... SNIP ...) /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/lib/jvm/java-8-oracle/bin:/usr/lib/jvm/java-8-oracle/db/bin:/usr/lib/jvm/java-8-oracle/jre/bin (... SNIP ...) Configuring env variables: {PATH=/home/rick/bin:/home/rick/.local/bin:/mnt/e/bin:/mnt/e/usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/lib/jvm/java-8-oracle/bin:/usr/lib/jvm/java-8-oracle/db/bin:/usr/lib/jvm/java-8-oracle/jre/bin, (... SNIP ...) 

This is what my system returns. Yours will likely be different. To make a long story short the culprit is /etc/profile.d/jdk.sh:

$ cat /etc/profile.d/jdk.sh
setenv J2SDKDIR /usr/lib/jvm/java-8-oracle
setenv J2REDIR /usr/lib/jvm/java-8-oracle/jre
setenv PATH ${PATH}:/usr/lib/jvm/java-8-oracle/bin:/usr/lib/jvm/java-8-oracle/db/bin:/usr/lib/jvm/java-8-oracle/jre/bin
setenv JAVA_HOME /usr/lib/jvm/java-8-oracle
setenv DERBY_HOME /usr/lib/jvm/java-8-oracle/db

You probably surmise /etc/profile.d/jdk.csh needs changing too. Indeed it contains the exact same contents as /etc/profile.d/jdk.sh

To address the XY problem

There is a better way than going through files line by line and changing an 8 to an 11.

The easiest method is using Java installer. From this Ask Ubuntu Q&A: Setting JDK 7 as default

To get a list of your installed Java platforms, run the following command from the terminal:

sudo update-alternatives --config java

This will give you a list output similar to this:

There are 2 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ 0 /usr/lib/jvm/java-6-oracle/jre/bin/java 1070 auto mode 1 /usr/lib/jvm/java-7-openjdk-i386/jre/bin/java 1051 manual mode
* 2 /usr/lib/jvm/java-6-openjdk-i386/jre/bin/java 1069 manual mode
Press enter to keep the current choice[*], or type selection number: 

The simplest place to set this is in .bashrc which can be done quickly this way:

echo JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64/ >> .bashrc

This will make it the last line read as bash initializes and should ensure that JAVA_HOME is correctly set. If you need to do something more complicated you'll want to read up a bit on how terminal initializes. I'd recommend you start by google-ing bashrc.

Try reading these answers in the link. They are regarding making environment variable changes persistent. I think whats happening is after you close the terminal they are reverting. Here's the link:Make Environment variable changes persist