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On Ubuntu 12.04 LTS I have installed Sun's JDK7, Eclipse, and the Arduino IDE. I want the Arduino to use OpenJDK 6 and want Eclipse to use Sun's JDK 7.

From my understanding I need to manually choose which Java to use before running each application. This led me to the update-java-alternatives -l command. When I run this I only see the following:

java-1.6.0-openjdk-amd64 1061 /usr/lib/jvm/java-1.6.0-openjdk-amd64

but when I run update-alternatives --config java I see the following:

*0  /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   auto mode
1  /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   manual mode
2  /usr/lib/jvm/jdk1.7.0/bin/java                   manual mode
3  /usr/lib/jvm/jre1.7.0/bin/java                   manual mode

I don't understand why the update-java-alternatives doesn't display the same 3 options. I also don't understand how to switch between OpenJDK6 and JDK7. How I can go about using the OpenJDK6 for Arduino development and Sun JDK7 for Eclipse/Android development?

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2 Answers 2

up vote 28 down vote accepted

sudo update-alternatives --config java

Configures the default for the program "java". That's the Java interpreter.

sudo update-alternatives --config javac

Configures the default Java compiler.

You can also see that, because the first command lists a lot of "JRE" (Java Runtime Environment) folders and the Program is just called "java".

If I check which version is being used by issuing the command java -version or javac -version

I can see, that each command changes the program being used. However, using update-java-alternatives with a JDK Version changes BOTH programs for me. Using the first commands, you can use a Java Interpreter and Java Compiler from different JDKs.

So it seems you need to install the openjdk-7-jdk package as well. It looks like you only installed openjdk-7-jre.

As for switching for different development environments. Well, either you switch manually each time, or maybe you can make the IDE select the javac version directly. Not sure about that, sorry. Maybe you can also work with environmental variables. But you should check with your development environments documentation.

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update-java-alternatives is a program to update alternatives for jre/jdk installations. update-alternatives is a symbolic link management system for linux (I'm sure there is little news here).

You can, and really should, use both update-java-alternatives and update-alternatives together.

Firstly, be sure to have the all the alternatives configured correctly. java and javac are but a few. There is javadoc, rmic, serialver and others. substituting the above variables for: native2ascii and /opt/jdk1.8.0_40/bin/native2ascii should report if the alternative is installed and/or selected.

When all the alternatives are configured you can then create links in /usr/lib/jvm to your manual instalation. In order to configure update-java-alternatives you must use a hidden file with the same name as your directory but preffixed by a . (dot).

Hope this helps.

Bibliography man -S 8 update-java-alternatives

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protected by Eric Carvalho Aug 23 at 19:35

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