If you have installed Ubuntu from scratch, most probably the java package is not installed by default. The java package is necessary to run any java-based app, including running java applets in the browser. While you may not use it it all the time, it is still handy to install it. When you need it, it is there ready to be used.
Sun JDK vs OpenJDK
In the past, Sun JDK was the default java package in Ubuntu. After Sun Microsystem was acquired by Oracle in 2010, Ubuntu (and various distros) switched the java package to the fully open-source OpenJDK as the SUN JDK no longer contain codes that are fully open-sourced.
OpenJDK is community-built and is (almost) 100% similar to the SUN JDK. You can easily install OpenJDK in Ubuntu via the Ubuntu Software Center, by clicking here or running the command:
sudo apt-get install openjdk-7-jre |
Personally, other than some minor font rendering issue with OpenJDK, I have not experience any major problem with OpenJDK. That could also because I don’t use many java-based apps in the first place. However, if you have a specific java-based app that don’t run well in OpenJDK, you can switch to the SUN JDK instead. Here is how you do it:
The hard way
This method requires you to install SUN JDK 7 manually. It is a good way for you to learn the trick.
1. Download the SUN JDK 7 here to your home folder.
2. Extract the tar file.
3. Move the extracted file to the “/usr/lib/jvm/” folder:
sudo mv jdk1.7.0_04 /usr/lib/jvm/ |
4. Install SUN JDK 7 in your system:
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_04/bin/javac 1 sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_04/bin/java 1 |
5. Set the environment variables:
sudo update-alternatives --config javac sudo update-alternatives --config java |
You will see an option like the screenshot below:
Enter the option that corresponds to the SUN JDK package. Press Enter.
That’s it.
To test your java:
java -version |
You should see something like this:
The easy way
If you don’t want to manually install the SUN JDK, you can do it via a PPA. Since there is no official PPA for SUN JDK, you will have to grab a custom PPA that comes with the java package. Note that custom PPAs might add extra software sources to the repository, and cause your system to be bloated or even have conflicts with other apps. So bear in mind the risk involved.
There are several PPAs out there that come with SUN JDK, one that you can use is “webupd8team/java”
sudo add-apt-repository ppa:webupd8team/java sudo apt-get update sudo apt-get install oracle-java7-installer |
This should install SUN JDK 7 in your system.
Run Java applet in Browsers (Firefox, Chrome etc)
Even after you have installed the java package, you will find that the java applet in your browser won’t run. If you are using the OpenJDK, here is another package that you need to install:
sudo apt-get install icedtea-7-plugin |
For Oracle java, run the commands:
mkdir ~/.mozilla/plugins ln -s /usr/lib/jvm/jdk1.7.0_04/jre/lib/i386/libnpjp2.so ~/.mozilla/plugins |
If you are using a 64-bit system, remember to change the “i386″ to “amd64“.
Once install, restart your browser. The java applet should run now. To test if Java is working in your browser, go to http://java.com/en/download/testjava.jsp. If installed correctly, you should see a “Your java is working” message.
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It’s not always so very easy with Java ! After downloading and extracting the jdk-7u4-linux-x64.tar.gz, moving it from my Downloads folder to /usr/lib/jvm, and installing it according to Damien’s «hard way» instructions, Synaptic shows that the following files are installed :
openjdk-6-jre
openjdk-6-jre-headless
openjdk-6-jre-lib
openjdk-7-jre
openjdk-7-jre-headless
openjdk-7-jre-lib
oracle-java7-installer
My question is – which, if any, these files can I uninstall, without negative consequences for my 64-bit Precise setup ? I can mention that upon running «java -version» in a terminal, I get the same result as Damien, above :
java version “1.7.0_04″
Java(TM) SE Runtime Environment (build 1.7.0_04-b20)
Java HotSpot(TM) 64-Bit Server VM (build 23.0-b21, mixed mode)
Henri
You can basically remove all the openjdk instances.
Thanks for your speedy reply, Damien ! What gives me pause is that when I attempt to uninstall the openjdk files, I am informed that even the relevant icedtea files will be removed :
icedtea-6-plugin
icedtea-plugin
icedtea6-plugin
icedtea-7-jre-cacao
icedtea-7-jre-jamvm
icedtea-7-jre-plugin
These files don’t seem to have anything to do with the oracle-java7-installer file, but still, on the precautionary principle, I’d like to ask if I can expect any problems if I uninstall all the icedtea as well as the openjdk files….
Thanks again for your kind help !
Henri
You can remove every instances of the icedtea plugin, since it is only meant for the openjdk packages. I have updated the article with instructions to configure the browser for Oracle Java. Check it out.
Thanks, Damien ! I uninstalled all the openjdk and icedtea packages, which freed something over 180 MB on my harddisk, and so far so good. something to keep in mind in October, when Quantal will be released, as I presume that the openjdk packages will be installed by default when upgrading….
Henri
I have installed ubuntu 12.04, Im trying to use an app that will not work with openjdk, I installed openjdk, now I can’t get rid of it, it wants to install openjdk 7 as I remove openjdk 6 in synaptic, help!
Install the SunJDK in your system and make it the default. After that, you should be able to uninstall the OpenJDK.
ok, what I did is sudo apt-get purge openjdk* following instructions from someone else, then I installed java using the ubuntu ppa. Everything seems to be working now as far as java is concerned.
thanks
You may try in your terminal:
sudo apt-get install default-jre
On my 12.04 it is not works
hi, tried earlier today to get my java converted to the sunjdk and wound up screwing up horribly, short story i’m on a fresh install of 12.04 (could i have fixed it some other way? don’t care.) followed the “hard way” instructions above, snagged at a typo (mine) but got past and finished install. java -version in the terminal gives the result shown as good above, but the testjava link indicates that java is not working. i find this odd given that the links in the sidebar are all showing fine now when during the process they were “pluggin needed” messages.
just trying to get runescape to work, have a bet to settle with a friend.
Perhaps you want to try the 32-bit jdk instead of 64-bit. I think that
Runescape has a compatibility issue with the 64-bit version.
I found the instructions at the bottom of this link helpful in cleaning out the old crap and getting FireFox to work with 1.7.0_06:
http://www.iasptk.com/ubuntu-oracle-java7-jdk7-jre7-firefox-chrome-plugin
You, sir, are a hero!
I finally have it working in no time thanks to your instructions!
Thanks a lot!
For some reason it says the file usr/lib/jvm doesn’t exist, do I have to make a new folder called jvm or is it something else? Please help I am a total noob when it comes to using linux.
Yes. If the jvm folder does not exist, you have to create it.
How can I debug a situation where the plugin does not work?
On the page
http://java.com/en/download/testjava.jsp
all I get is “error! click for details”
and when i click something says NullpointerException.
One question. If we install java via ‘The hard way’ as described, how do we get notified of updates to the JDK?
you won’t be notified. The only way is to check out sun jdk website regularly for update.
Thanks for this post. It was very helpful to me. Just one remark though. The symbolic link is wrong. Should be (for 64bit):
ln -s /usr/lib/jvm/java-7-oracle/jre/lib/amd64/libnpjp2.so ~/.mozilla/plugins
Good Open JDK did not work. Had to use evil Sun JDK. Great tutorial! A real life saver.