Hello,

I just installed Centos5, and now I need to install java.
It seems that Centos5 creates many directories for java and many sym links, for instance there are java directories in /etc/, /etc/alternatives/, /usr/share/, /usr/lib/

Do I need those directories?
How do I install Java 1.6 ?

Thanks a lot

Review:

http://java.sun.com/javase/6/webnotes/install/jdk/install-linux.html#install-rpm

http://plugindoc.mozdev.org/faqs/java.html

And this may prove helpful;

Reconfiguring the default Java configuration for Red Hat / Fedora

This is done as root or equivalent.

First remove /var/lib/alternatives/java file by typing;

rm /var/lib/alternatives/java

When asked press the 'y' key,

Now to create the new (corrected) alternatives file for java type
the following commands as root;

/usr/sbin/alternatives --install /usr/bin/java java /usr/lib/jvm/jre-1.4.2-gcj/bin/java 1

For jre:

/usr/sbin/alternatives --install /usr/bin/java java /usr/java/jre1.6.0/bin/java 2

For jdk:

/usr/sbin/alternatives --install /usr/bin/java java /usr/java/jdk1.6.0/bin/java 2

/usr/sbin/alternatives --config java

You should now see for example:

There are 2 programs which provide 'java'.

Selection Command
-----------------------------------------------
1 /usr/lib/jvm/jre-1.4.2-gcj/bin/java
*+ 2 /usr/java/jre1.6.0/bin/java

Enter to keep the current selection[+], or type selection number:

Type: <choose 1 or 2>

In the example above java is already configured correctly [*+ 2] to
use Sun's Java, no changes are needed, just press the Enter key here.
If you have been following the instructions then you should have
the same results (version numbers may be sightly different).

Now type; /usr/sbin/alternatives --display java

You should see for example;

java - status is manual.
link currently points to /usr/java/jre1.6.0/bin/java
/usr/lib/jvm/jre-1.4.2-gcj/bin/java - priority 1
/usr/java/jre1.6.0/bin/java - priority 2
Current `best' version is /usr/java/jre1.6.0/bin/java.

Next you might want to create (or edit) /etc/profile.d/java.sh
file, examples below:

For jre;

export JAVA_HOME="/usr/java/jre1.6.0/bin"
export JAVA_PATH="$JAVA_HOME"
export PATH="$PATH:$JAVA_HOME"

For jdk;

export JAVA_HOME="/usr/java/jdk1.6.0/jre/bin"
export JAVA_PATH="$JAVA_HOME"
export PATH="$PATH:$JAVA_HOME"


When done creating or editing the file type;

source /etc/profile.d/java.sh

Now any user root or other wise should be able to use the command;

which java

and the results should read something like;

/usr/bin/java

Also any user root or other wize should be able to use the command;

java -version

and the results should read something like;

java version "1.6.0"
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode, sharing)

Hello,

Thanks a lot for your help, now everything works fine.

One more (silly) question, what is the purpose of those 'alternatives'?

Thanks again for your fast help

Arturo

First, your welcome, glad to help.

In answer to guestion, so Sun's java gets configured properly for use with CentOS. you can find more about the alternatives by typing from the virtual console or xterm session: man alternatives

I followed your instructions perfectly (well i think it is perfectly, i double checked all your instructions and checks and it looks the same), but all my java apps still appear blank in mozilla.

It does not give the install missing plug error or anything, they just show as blank spaces.

any ideas/clues?

well that kinda sucks, i cannot find the edit button, so ill say it here-

it is now working after a full system reboot lol

Have you checked the following url?
I found it very helpful. Gives you step by step instruction as to install JDK on centOS.
How to install Java on CentOS 4 and CentOS 5