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I use ArchLinux, and an IDE called PyCharm. On its download page, it recommends using Java 6 instead of OpenJDK. ArchLinux has an OpenJDK package (jdk7-openjdk) that I have installed, installed, and from what I had read in the Arch Wiki on Java, it should be possible to install Oracle Java 6 along side OpenJDK 7 via a packages called jdk6-compat and jre6-compat, which install these versions of Java in /opt/ instead of the normal location.

However, after installing jdk6-compat and jre6-compat, I still see that I am running OpenJDK 7 when I run the following:

% java -version
java version "1.7.0_09"
OpenJDK Runtime Environment (IcedTea7 2.3.3) (ArchLinux build 7.u9_2.3.3-1-x86_64)
OpenJDK 64-Bit Server VM (build 23.2-b09, mixed mode)

...even after I have set JAVA_HOME and added /opt/java6/bin to my PATH in my .zshrc file.

How can I get PyCharm (or other applications) to use Oracle Java 6 instead of OpenJDK?

Thanks, and apologies if I've posted in the wrong place.

Other information that might be helpful:

  • Using Gnome 3 as DE
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2 Answers 2

Reset to default
9

ArchLinux keeps the different JDKs in the /usr/lib/jvm directory, changing the default JDK is a matter of modifying the symbolic links there:

# ls -al /usr/lib/jvm  
lrwxrwxrwx   1 root root     14 May 31 19:58 default -> java-8-openjdk
lrwxrwxrwx   1 root root     18 May 31 19:58 default-runtime -> java-8-openjdk/jre
drwxr-xr-x   7 root root   4096 May 27 21:45 java-10-openjdk
drwxr-xr-x   6 root root   4096 May 31 14:35 java-8-openjdk
drwxr-xr-x   7 root root   4096 May 31 19:56 java-9-openjdk

Arch has a special script for that:

# archlinux-java set java-10-openjdk

and you get:

# java -version
openjdk version "10.0.1" 2018-04-17
OpenJDK Runtime Environment (build 10.0.1+10)
OpenJDK 64-Bit Server VM (build 10.0.1+10, mixed mode)

you can also use the 'fix' and 'status' options:

# archlinux-java fix
# archlinux-java status
Available Java environments:
  java-10-openjdk (default)
  java-8-openjdk
  java-9-openjdk
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2
7

If I want to use a different version of Java I do two things:

  • First, set JAVA_HOME as appropriate for that installation of Java and export it.
  • Then, update my path with `PATH=${JAVA_HOME}/bin:${PATH}.

Due to the way the PATH is searched, if you add to end of the path, the new version won't be used. Anything added to the end of the path only adds new commands, it does not replace existing commands. Prepending to the PATH variable will use command in the new directory in preference to other command.

Commands like java often involve a number of symbolic links before you get to the program. Using ${JAVA_HOME}/bin bypasses any indirections, and provides a direct path to the various Java related commands.

EDIT: If you want to run only certain programs with a different version of Java you could use a wrapper like this:

#!/bin/bash
# javawrapper - replace Java for a command.
export JAVA_HOME=$1; shift
PATH=${JAVA_HOME}/bin:$PATH
$*

You can then call the wrapper with a command like. 

javawrapper /opt/java6 PyCharm

You could also add an alias to your ~/.bashrc file like this

alias PyCharm='javawrapper /opt/java6 PyCharm'
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2
  • Well, that solves half the problem; I was appending to the end, rather than the beginning of $PATH. But how do I only run the different version of Java for certain applications? Commented Nov 17, 2012 at 18:43
  • I've updated my response. However, in a case like yours, I have rarely need to keep programs using the default Java version. Commented Nov 17, 2012 at 19:06

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