3

I am running Ubuntu 16.04. I have downloaded JDK 7.0 from Oracle website and untar'ed and put it in a folder /opt/JDK/, such that the final install directory is /opt/JDK/jdk1.7.0_80 Then I executed the following commands given in this SO answer:

update-alternatives --install /usr/bin/java java /opt/jdk1.8.0/bin/java 1
update-alternatives --install /usr/bin/javac javac /opt/jdk1.8.0/bin/javac 1
update-alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so mozilla-javaplugin.so /opt/jdk1.8.0/jre/lib/amd64/libnpjp2.so 1
update-alternatives --set java /opt/jdk1.8.0/bin/java
update-alternatives --set javac /opt/jdk1.8.0/bin/javac
update-alternatives --set mozilla-javaplugin.so /opt/jdk1.8.0/jre/lib/amd64/libnpjp2.so

I want to set the JAVA_HOME environment variable. I know how to do it using /etc/environment. The confusion is which path to use.

Should I use /usr/bin/java?

Or should I use /opt/JDK/jdk1.7.0_80?

Or should I use /opt/JDK/jdk1.7.0_80/bin?

The output of update-alternatives --config java is:

There is 1 choice for the alternative java (providing /usr/bin/java).

  Selection    Path                           Priority   Status
------------------------------------------------------------
  0            /opt/JDK/jdk1.7.0_80/bin/java   1         auto mode
* 1            /opt/JDK/jdk1.7.0_80/bin/java   1         manual mode

Press <enter> to keep the current choice[*], or type selection number:
2

As you can see two alternatives are identical, so you can use both of them. Simply you can use following command to set JAVA_HOME:

JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")

The command update-alternatives --config java is used when you have different JAVA installed on your machine. For example Mine is as follow:

There are 2 choices for the alternative java (providing /usr/bin/java).

* 0            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      auto mode
  1            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode
  2            /usr/lib/jvm/java-8-oracle/jre/bin/java          1081      manual mode
| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.