set up java things in ubuntu

JDK INSTALLATION

No need to argue, just use 'apt-get' things :

sudo apt-get update

for java 5

sudo apt-get install sun-java5-jre sun-java5-jdk

for java 6

sudo apt-get install sun-java6-jre sun-java6-jdk

verify ur installation

java -version

java version "1.6.0_06"
Java(TM) SE Runtime Environment (build 1.6.0_06-b02)
Java HotSpot(TM) Server VM (build 10.0-b22, mixed mode)

to list all ur java installed

sudo update-java-alternatives -l

java-1.5.0-sun 53 /usr/lib/jvm/java-1.5.0-sun
java-6-sun 63 /usr/lib/jvm/java-6-sun

to change ur default java

sudo update-alternatives --config java


SETTING JAVA ENV

edit this file

sudo vi /etc/environment

add line

# java 5
export JAVA_HOME=/usr/lib/jvm/java-1.5.0-sun

# java 6
#export JAVA_HOME=/usr/lib/jvm/java-6-sun

# tomcat 5
export CATALINA_HOME=/data/java/jakarta-tomcat-5.0.18

save ur file and logout

check ur env with

env | grep JAVA_HOME
env | grep CATALINA_HOME