JAVA_HOME and PATH are set but java -version still shows the old one

While it looks like your setup is correct, there are a few things to check:

1. The output of env - specifically PATH.
2. command -v java tells you what?
3. Is there a java executable in $JAVA_HOME\bin and does it have the execute bit set? If not chmod a+x java it.

I trust you have source'd your .profile after adding/changing the JAVA_HOME and PATH?

Also, you can help yourself in future maintenance of your JDK installation by writing this instead:

export JAVA_HOME=/home/aqeel/development/jdk/jdk1.6.0_35export PATH=$JAVA_HOME/bin:$PATH

Then you only need to update one env variable when you setup the JDK installation.

Finally, you may need to run hash -r to clear the Bash program cache. Other shells may need a similar command.

Cheers,

update-java-alternatives

The java executable is not found with your JAVA_HOME, it only depends on your PATH.

update-java-alternatives is a good way to manage it for the entire system is through:

update-java-alternatives -l

Sample output:

java-7-oracle 1 /usr/lib/jvm/java-7-oraclejava-8-oracle 2 /usr/lib/jvm/java-8-oracle

Choose one of the alternatives:

sudo update-java-alternatives -s java-7-oracle

Like update-alternatives, it works through symlink management. The advantage is that is manages symlinks to all the Java utilities at once: javac, java, javap, etc.

I am yet to see a JAVA_HOME effect on the JDK. So far, I have only seen it used in third-party tools, e.g. Maven.

If you want to use JDKs downloaded from Oracle's site, what worked for me (using Mint) is using update-alternatives:

1. I downloaded the JDK and extracted it just anywhere, for example in /home/aqeel/development/jdk/jdk1.6.0_35

2. I ran:

   sudo update-alternatives --install /usr/bin/java java /home/aqeel/development/jdk/jdk1.6.0_35/bin/java 1

   Now you can execute sudo update-alternatives --config java and choose your java version.

3. This doesn't set the JAVA_HOME variable, which I wanted configured, so I just added it to my ~/.bashrc, including an export JAVA_HOME="/home/aqeel/development/jdk/jdk1.6.0_35" statement

Now, I had two JDKs downloaded (let's say the second has been extracted to /home/aqeel/development/jdk/jdk-10.0.1).

How can we change the JAVA_HOME dynamically based on the current java being used?

My solution is not very elegant, I'm pretty sure there are better options out there, but anyway:

4. To change the JAVA_HOME dynamically based on the chosen java alternative, I added this snippet to the ~/.bashrc:

   export JAVA_HOME=$(update-alternatives --query java | grep Value: | awk -F'Value: ' '{print $2}' | awk -F'/bin/java' '{print $1}')

Finally (this is out of the scope) if you have to change the java version constantly, you might want to consider:

5. Adding an alias to your ~./bash_aliases:

   alias change-java="sudo update-alternatives --config java"

(You might have to create the file and maybe uncomment the section related to this in ~/.bashrc)