Introduction
Java
is a technology from Oracle (formerly: Sun Microsystems). There are
several implementations, of which five will be discussed here:
- OpenJDK: The primary goal of the OpenJDK project is to produce an open-source implementation of the Java SE Platform (6 and 7). This is the default version of Java that Ubuntu uses and is the easiest to install.
- Oracle (Sun) Java 6: Oracle (Sun) Java 6 is the reference implementation for Java 6.
- Oracle Java 7: Oracle Java 7 is Oracle's own version of Java 7.
- IBM Java: IBM Java is the preferred Java solution on PowerPC machines. It is a reimplementation of Java with a Just-In-Time Compiler. It is only available from IBM's website.
- GNU Compiler: A Java compiler made by GNU. Only developers should have to install this.
OpenJDK
Installation of Java Runtime Environment
- Install the openjdk-6-jre package using any installation method.
- Install the openjdk-7-jre package using any installation method.
Browser plugin
- Install the icedtea6-plugin package using any installation method.
- Install the icedtea-7-plugin package using any installation method.
This plugin works with the main browsers: Firefox, Chromium, Google Chrome, and Epiphany.
On Konqueror, go to Settings → Configure Konqueror... and from menu select Java & JavaScript, then tick Enable Java globally option.
SDK (Software Development Kit)
In Java parlance the Java Development Kit (JDK) is sometimes used for SDK. (More about that here.)
- Install the openjdk-6-jdk package using any installation method.
- Install the openjdk-7-jdk package using any installation method.
Alternative Virtual Machines
Most users won't need to worry about these, but if you use an architecture (e.g. PowerPC) that defaults to the Zero Virtual Machine (VM), then you may see a significant performance increase if you switch to:
- JamVM: This is the default VM for ARM in 11.10. Install the icedtea-6-jre-jamvm package if available. If it is not, then compile instructions can be found here.
- Cacao: Ensure the icedtea-6-jre-cacao package is installed.
- Zero/Shark: Shark is a just-in-time (JIT) compiler for Zero. Install the openjdk-6-jre-zero package if available. On architectures which use the Zero VM as the default, the openjdk-6-jre-zero package contains the Shark VM.
To use a different VM other than the default, just add the appropriate option to the command you normally use. For example:
java -jamvm|-cacao|-shark|-zero -version
See the file /usr/lib/jvm/java-6-openjdk-powerpc/docs/README.Debian
(or its equivalent) and the other documents in that directory for more
information. Note, the IcedTea browser plugin will use the default VM
(which you can change in the file /etc/java-6-openjdk/jvm.cfg).
Oracle Java 7
Oracle has declared Java 7 to be fit for general use.
Currently
there are no .deb packages available for Oracle Java 7. The raw
binaries (without installer) can be downloaded directly from Oracle (Oracle Java download page).
Installing Oracle Java 7 by a script or from the command line
You
can install the newest and secure Oracle (Sun) Java 7 by a script (JRE
only) or by a command line method. Both are easy to apply.
Script (JRE only)
Only
supports Oracle (Sun) Java 7 JRE (which covers the needs of 99 % of all
computer users). It pulls the packages from Oracle's website and
installs them, comparable to the way Adobe Flash Player is being
installed. Plus it adds a dedicated repository, from which you'll
receive updates automatically.
Command line methods
Do-it-yourself methods, but very easy to apply (basically: you copy/paste some terminal commands).
- http://sites.google.com/site/easylinuxtipsproject/java (for JRE, more extensive explanation of the commands than in askubuntu.com)
Using
webupd8.org's method has a great benefit in that the package will be
updated as Oracle releases Java updates, which means that there will be
no need to keep track of updates and reinstall them manually.
A note (hopefully temporary) about the Eugene San PPA for those who are attempting to use it and are having issues:
As of the time of this entry, the eugenesan/java PPA is broken. If
you have attempted to use it, you may do the following to remove it and
use webupd8.org's PPA method (above) instead
sudo apt-get purge oracle-java7-installer* sudo apt-get install ppa-purge sudo ppa-purge ppa:eugenesan/java sudo apt-get clean sudo apt-get update
If
the preceding does not work, you may try the following more aggressive
method. Be aware, however, that it uses the rm command, which will
completely remove files immediately and permanently from an important
directory. Be extremely cautious.
sudo rm /var/lib/dpkg/info/oracle-java7-installer* sudo apt-get purge oracle-java7-installer* sudo rm /etc/apt/sources.list.d/*java* sudo apt-get update
There is also an RFE opened on Oracle bugtracker to provide the debian package/installer for Java 7. Please consider voting for this RFE.
Oracle (Sun) Java 6
WARNING:
Oracle Java 6 had reached its end of life in November 2012. There is at
least one severe known vulnerability in this version, and since Java 6
is neither supported by Canonical nor Oracle, there may be many more!
You should really not install this unless you have a specific need to do
so. It is recommended that users either migrate to OpenJDK, or install
Oracle Java 7.
Oracle (Sun) Java 6 is no longer available to be distributed by Ubuntu, because of license issues.
Deprecated information about the installation of Oracle Java 6:
JDK or JRE
Downloads the Java binary installers from Oracle, builds the .deb packages locally on your computer and then installs them. Packages are compatible with the “official” Ubuntu ones and will upgrade Java 6 that was previously installed from packages.
You can find the script and full usage instructions on github.
(since version 0.2.3 it also works with java 7 using -7 optional parameter).
Another instruction it works for Ubuntu 12.04.
Manual method
- oracle java 6 jre 32-bit
$ wget http://download.oracle.com/otn-pub/java/jdk/6u34-b04/jre-6u34-linux-i586.bin $ chmod u+x jre-6u34-linux-i586.bin $ ./jre-6u34-linux-i586.bin $ sudo mkdir -p /usr/lib/jvm $ sudo mv jre1.6.0_34 /usr/lib/jvm/ $ sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jre1.6.0_34/bin/java" 1 $ sudo update-alternatives --install "/usr/lib/mozilla/plugins/libjavaplugin.so" "mozilla-javaplugin.so" "/usr/lib/jvm/jre1.6.0_34/lib/i386/libnpjp2.so" 1 $ sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jre1.6.0_34/bin/javaws" 1
or
- oracle java 6 jdk 64-bit
$ wget --no-cookies --header "Cookie: gpw_e24=http%3A%2F%2Fwww.oracle.com%2F" http://download.oracle.com/otn-pub/java/jdk/6u45-b06/jdk-6u45-linux-x64.bin $ chmod u+x jdk-6u45-linux-x64.bin $ ./jdk-6u45-linux-x64.bin $ sudo mv jdk1.6.0_45 /opt $ sudo update-alternatives --install "/usr/bin/java" "java" "/opt/jdk1.6.0_45/bin/java" 1 $ sudo update-alternatives --install "/usr/bin/javac" "javac" "/opt/jdk1.6.0_45/bin/javac" 1 $ sudo update-alternatives --install "/usr/lib/mozilla/plugins/libjavaplugin.so" "mozilla-javaplugin.so" "/opt/jdk1.6.0_45/jre/lib/amd64/libnpjp2.so" 1 $ sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/opt/jdk1.6.0_45/bin/javaws" 1
- IMPORTANT choose the java you installed as default
$ sudo update-alternatives --config java $ sudo update-alternatives --config javac
Optionally you can set a JAVA_HOME env variable:
export _JAVA_HOME=/opt/jdk1.6.0_45/
Choosing the default Java to use
If
your system has more than one version of Java, configure which one your
system uses by entering the following command in a terminal window
sudo update-alternatives --config java
This will present you with a selection that looks similar to the following (the details may differ for you):
There are 2 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ———————————————————— * 0 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 auto mode 1 /usr/lib/jvm/jre1.7.0/jre/bin/java 3 manual mode Press enter to keep the current choice[*], or type selection number: 1
IBM Java
IBM provide JRE and SDK binaries for a number of architectures, including PowerPC. These are available via the IBM Downloads Page once you have registered.
There
are two types of 'InstallAnywhere' package available to you: the
'Archive/tgz' only extracts the files to your system, whereas the
'Installable' package supposedly also configures your system. You can
use either, both require additional configuration with Ubuntu. The
'Installable' package also provides an uninstall option.
To run the downloaded file use the following commands:
chmod a+x ibm-java-ppc-jre-6.0-10.1.bin sudo ./ibm-java-ppc-jre-6.0-10.1.bin
This
launches an interactive program that guides you through the
installation options. Extract the file to the directory of your choice
(for example /usr/lib/jvm/java-6-ibm-powerpc).
Once
completed, you then need to tell the system where to find the new java
commands. If you only have IBM Java installed then you can define an environment variable to do this. For example, add the following line to your .bashrc file in your home directory.
export PATH=/usr/lib/jvm/java-6-ibm-powerpc/bin:/usr/lib/jvm/java-6-ibm-powerpc/jre/bin:$PATH
If you also have openjdk installed then you'll need to update the java alternatives:
sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/java-6-ibm-powerpc/jre/bin/java" 1 sudo update-alternatives --set java /usr/lib/jvm/java-6-ibm-powerpc/jre/bin/java
You'll need to repeat this for every command you need. For the mozilla plugin you can use:
sudo update-alternatives --install /usr/lib/mozilla/plugins/mozilla-javaplugin.so mozilla-javaplugin.so /usr/lib/jvm/java-6-ibm-powerpc/jre/lib/ppc/libnpjp2.so 1 sudo update-alternatives --config mozilla-javaplugin.so
Further guidance can be found in the IBM documentation (including a different way to link the plugin).
If
you don't use the mozilla plugin frequently then you can disable it for
security. You can do this through the Firefox menus or there are
Firefox extensions you can use to automate this.
To control which Java the Konqueror web browser uses, go to your KDE system settings. Select Internet & Network -> Web Browser -> Java & JavaScript, and change the Path to Java executable to either /usr/lib/jvm/java-6-ibm-powerpc/bin/java or java (without any quotes).
Test the installation at the Sun Java test webpage and using the command:
java -version
Note, there are old PowerPC deb packages still in medibuntu
(keep clicking refresh if you get 403 forbidden). These are probably
the easiest way to install, although they are now lacking security
updates, plus the latest browser plugin. For these reasons it is
strongly advised that you download a newer Service Refresh Fix Pack directly from the IBM Downloads Page.
You may have to install libstdc++5 and libgtk1.2
packages to use old versions of IBM Java. If you installed a 1.4.2
version, and your processor is not a G5, you may have to perform another
step to get it to work. For a G3 or G4, use the following command:
sudo sh -c 'echo "JITC_PROCESSOR_TYPE=6" >> /etc/environment'
For a 604e or 603e, instead use:
sudo sh -c 'echo "JITC_PROCESSOR_TYPE=5" >> /etc/environment'
You will have to log out or restart the computer for this to take effect.
GNU Compiler for Java
Install the java-gcj-compat-headless package using any installation method.
To install the development environment, install the java-gcj-compat-dev package using any installation method.
GCJ
is a front end to the GCC compiler which can natively compile both
Java(tm) source and bytecode files. The compiler can also generate class
files. Gcjwebplugin is a little web browser plugin to execute Java applets.
It
is targeted for Mozilla and compatible browsers that support the NPAPI.
Others include the Eclipse Java Compiler, which is maintained by the Eclipse Foundation.
Eclipse is an open-source Integrated development environment (IDE)
written primarily in Java. The Eclipse open source community has over 60
open source projects. OpenJDK is the open source Java, derived from
sources which will become OpenJDK 7 in the future.
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