More on Java Installation

http://www.linuxquestions.org/questions/showthread.php?t=525948

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/jre/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:

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)

That's it, all done.

See not that hard to change.