This is an old revision of the document!
Table of Contents
Java Runtime Environment (JRE)
The Java Runtime Environment (JRE) is needed to run Java applications.
The JRE does not contain development tools. You need the Java Development Kit (JDK) or a comparable solution to develop Java applications.
Terms
JRE
Java Runtime Environment. Needed to run Java applications on your platform. There are Open Source JREs and the “original” JRE by Oracle (former Sun Microsystems).
JVM
Java Virtual Machine. Part of the JRE, executes the Java code you want to run.
JDK
Java Development Kit (JDK). A development tool needed by programmers to compile Java programs. The JDK brings the complete JRE – if you want to install the JDK, there is no need to install the JRE separately. There are Open Source JDKs and the “original” JDK by Oracle (former Sun Microsystems).
Java SDK
Java Software Development Kit, a synonym for the JDK.
Installation
Ubuntu
10.04 Lucid and above
You can choose between two1) Open Source JREs and the “original” JRE by Oracle (former Sun Microsystems).
If you don't know which JRE to choose, take the one by Oracle/Sun to be on the safe side – some rare applications simply do not work without the proprietary one. Additionally, some users may have to run applications which are certified for the Oracle JRE only, loosing support if they use another JRE.
Oracle Java (former Sun Java)
If not already done, you have to add the partner repository first.
Simply install the following package(s):
sun-java6-jre
(partner)
There are some additional packages, providing special functionality:
sun-java6-plugin
(partner) – Java plugin for your webbrowser. Needed to run Java Applets on websites.
OpenJDK
Simply install the following package(s):
openjdk-6-jre
(universe)
Windows
XP and above
The only really usable JRE on Windows systems is the proprietary JRE by Oracle (sometimes called “Java SE Runtime Environment”). Simply download the Windows installer and execute it with administrator privileges.
Watch out for the Yahoo! and/or Google Browser Toolbar or other software you may not want. The Java installer tries to install such 3rd party components by default. This is also important for Java Updates. (data as per 2010-07-06)
Tips and tricks
Choosing the default JRE (Ubuntu Linux)
Even it is not recommended to install more than one JRE, it is possible to have e.g. the OpenJDK JRE and Oracle Java JRE installed at the same time on the same machine. To choose the default one called by java
on your command line, run the following:
sudo update-alternatives --config java
Weblinks
- Java testing page from Oracle.