How to Install Java Runtime In Ubuntu 12.04

Ref:   How to Install Java Runtime In Ubuntu 12.04

If you have installed Ubuntu from scratch, most probably the java packageis not installed by default. The java package is necessary to run anyjava-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. Whenyou 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 SunMicrosystem was acquired by Oracle in 2010, Ubuntu (and various distros) switched the java package to the fully open-source OpenJDK as the SUNJDK no longer contain codes that are fully open-sourced.

OpenJDKis community-built and is (almost) 100% similar to the SUN JDK. You caneasily install OpenJDK in Ubuntu via the Ubuntu Software Center, byclicking here or running the command:

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1. sudo apt-get install openjdk-7-jre

Personally, other than some minor font rendering issue with OpenJDK, I have notexperience any major problem with OpenJDK. That could also because Idon’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 switchto 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:

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1. udo mv jdk1.7.0_04 /usr/lib/jvm/

4. Install SUN JDK 7 in your system:

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1. sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_04/bin/javac 1
   
2. sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_04/bin/java 1

5. Set the environment variables:

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1. 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:

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1. 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 aPPA. 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 PPAsmight add extra software sources to the repository, and cause yoursystem to be bloated or even have conflicts with other apps. So bear inmind the risk involved.

There are several PPAs out there that come with SUN JDK, one that you can use is “webupd8team/java”

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1. sudo add-apt-repository ppa:webupd8team/java
   
2. sudo apt-get update
   
3. 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 javaapplet in your browser won’t run. If you are using the OpenJDK, here isanother package that you need to install:

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1. sudo apt-get install icedtea-7-plugin

For Oracle java, run the commands:

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1. mkdir ~/.mozilla/plugins
   
2. 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.