Need Help on JAVA_HOME, CLASSPATH set up

[DapperDrakeNewbieDR]

I need step-by-step instructions on how to set up the JAVA_HOME and CLASSPATH variables. Can anyone help me out with this issue?

Thanks in advance.

[tedwardo2]

it depends on what implementation of java you have installed, where it is installed, and a number of other things.

If you already know what you want to set JAVA_HOME and CLASSPATH to, you can just run
sudo gedit /etc/environment
and then add a line for each variable.

[DapperDrakeNewbieDR]

Thanks tedwardo2, it worked perfectly fine.

See you around.

[DapperDrakeNewbieDR]

This is the output of the "etc/environment" file after I "gedit" it,


PATH="/usr/local/Java/jdk1.5.0_07/bin:.:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11:/usr/games"
LANG="en_AU.UTF-8"
LANGUAGE="en_AU:en"
JAVA_HOME="/usr/local/Java/jdk1.5.0_07"
CLASSPATH="/usr/local/Java/jdk1.5.0_07/lib:."


It may serve you as a guide to you folks looking for help.

[erpa]

i'm having the same problem, but i don't know exactly what to do. i installed jdk and jre trough apt-get but i can't find "/usr/local/Java/jdk1.5.0_07/bin:." or any of the others path you used.
The best i was able to do was to find the java folder in usr/share but i can't find anything like jdk1.5.0_07/bin:. in it. This is the content of the java folder :

http://img527.imageshack.us/img527/1743/pippo2rn3.th.png (http://img527.imageshack.us/my.php?image=pippo2rn3.png)

wich path should i use? doi need to install somtging else? atm the content of my etc/environment is:

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"
LANG="it_IT.UTF-8

thx in advice for help

P.S. sry for may bad english

[steve.horsley]

The easiest way to find it is to use the command
whcih java
which probably says /usr/bin/java, but this is a symlink. if you do
ls -l /usr/bin/java
it will tell you where it links to (probably another symlink). Keep on followinf the symlinks until you find the real executable. It's there somewhere.

If you install java straight from Sun, it defaults into /opt/java..., but the Ubuntu packagers tend to put java in /usr/lib or /usr/share or something like that.

P.S.
With the Sun JRE, you don't normally need to set JAVA_HOME or CLASSPATH at all.

[akhilanger]

If you have installed java through sudo apt-get install ......
then it is installed in /usr/lib/jvm

[bwakkie]

euhm.. is my case:

which java
/usr/bin/java

ls -l /usr/bin/java
/usr/bin/java -> /etc/alternatives/java

ls -l /etc/alternatives/java
/etc/alternatives/java -> /usr/lib/jvm/java-gcj/jre/bin/java

Changed that to:
java -> /usr/lib/jvm/java-6-sun-1.6.0.06/jre/bin/java


then I added the following line to /etv/environment:
JAVA_HOME="/usr/lib/jvm/java-6-sun-1.6.0.06/"

and created the following symlink:
/usr/java/jdk -> /usr/lib/jvm/java-6-sun-1.6.0.06/

although I have both... java is sooooo confusing!!

[elnur]

Changed that to:
java -> /usr/lib/jvm/java-6-sun-1.6.0.06/jre/bin/java

and created the following symlink:
/usr/java/jdk -> /usr/lib/jvm/java-6-sun-1.6.0.06/


You really shouldn't. Just run this command:

sudo update-java-alternatives -s java-6-sun


It will set java-6-sun to be run by default.

[Juzz]

You really shouldn't. Just run this command:

sudo update-java-alternatives -s java-6-sun


It will set java-6-sun to be run by default.

Why does java on linux have to be so obscure?

I was wondering why my netbank didn't work anymore - but when I ran java --version gcj had stolen my settings from sun being default...

Even after running that command to set java alternatives firefox hangs and uses up 100% cpu time when trying to access my netbank :(

[cl333r]

Why does java on linux have to be so obscure?
Historically due to licensing issues we had to install by default the gcj version which nobody took for serious including developers. Fortunately Java is (for a few years) on it's path to getting fully open source and the gcj version has been replaced with the openjdk version, which being better isn't yet as qualitative as the closed source one. But this continues changing to the better although no one can tell you when the day comes when openjdk is as good as the current closed version. There are plans to achieve this parity for Java 7.

[Pathan]

You really shouldn't. Just run this command:

sudo update-java-alternatives -s java-6-sun


It will set java-6-sun to be run by default.

Thanks mate it worked like a charm for me. :D I was unable to run a small monitoring application since 3 days. Thanks again

[Zannax]

You really shouldn't. Just run this command:

sudo update-java-alternatives -s java-6-sun


It will set java-6-sun to be run by default.

Thank you so much! :) I was stuck trying to install a software I absolutely need (personal income declaration) and it didn't work: I had no guess that gij was the problem. Now works like a charm!

[elnur]

Thank you so much! :) I was stuck trying to install a software I absolutely need (personal income declaration) and it didn't work: I had no guess that gij was the problem. Now works like a charm!

You are totally welcome. :)

[alex.scotton]

AWESOME.... I have been messing with java for an hour or so until i stumbled across:
sudo update-java-alternatives -s java-6-sun

Now to continue getting my own google wave server up and running haha... had to compile it with ant :-P

[franciskus]

I am facing a similar problem, when I try to run an application using Netbeans I receive a message that an specific package was not found.

I suppose it's because java is not finding the .jar in the classpath:
private com.toedter.calendar.JDateChooser dataInicioFaturamento;
/home/francisco/NetBeansProjects/SikLami/src/com/sikgraf/ui/reports/ListagemFaturamentoUI.java:80: package com.toedter.calendar does not exist
This package is in the file jcalendar-1.3.2.jar, which is in /home/francisco/Sistemas/lib10anos folder.

And I have my environment file as following:
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"
JAVA_HOME="/usr/lib/jvm/java-6-sun/jre"
CLASSPATH="/home/francisco/Sistemas/lib10anos:.:/home/francisco/Sistemas/lib10anos/jcalendar-1.3.2.jar"
Shouldn't be everything working correctly???

Appreciate any help.
F.

[ubundom]

Hi folks, I am trying to run (Serena) OpenProj [aka Projity] and it complains that it cannot find the saxon9-dom.jar:

~$ openproj
Java auto-detection...
Checking java
Java version: 1.6.0_15 OK
Java implementation: Java(TM) OK
Java OK
Error
DOMSource cannot be processed: check that saxon9-dom.jar is on the classpath
Exception in thread "main" java.lang.AssertionError: net.sf.saxon.trans.XPathException: DOMSource cannot be processed: check that saxon9-dom.jar is on the classpath
at java.util.prefs.XmlSupport.writeDoc(XmlSupport.jav a:262) ...

<more stuff>

... at net.sf.saxon.IdentityTransformer.transform(Identit yTransformer.java:29)
at java.util.prefs.XmlSupport.writeDoc(XmlSupport.jav a:259)
... 17 more
Error
DOMSource cannot be processed: check that saxon9-dom.jar is on the classpath
Exception in thread "Thread-1" java.lang.AssertionError: net.sf.saxon.trans.XPathException: DOMSource cannot be processed: check that saxon9-dom.jar is on the classpath
at java.util ...

<more stuff>

... Caused by: net.sf.saxon.trans.XPathException: DOMSource cannot be processed: check that saxon9-dom.jar is on the classpath
at net.sf.saxon.event.Sender.send(Sender.java:226)
at net.sf.saxon.IdentityTransformer.transform(Identit yTransformer.java:29)
at java.util.prefs.XmlSupport.writeDoc(XmlSupport.jav a:259)
... 19 more
~$

But it seems to me that the saxon9-dom.jar is on the CLASSPATH:

~$ locate saxon9-dom
/usr/share/Kernow/lib/saxon9-dom.jar

~$ ls -al /usr/share/Kernow/lib/saxon9-dom.jar
-rw-r--r-- 1 root root 129212 2010-01-31 21:06 /usr/share/Kernow/lib/saxon9-dom.jar

~$ echo $CLASSPATH
/usr/share/Kernow/lib/saxon9-dom.jar

~$

[dilantha]

Hi All,

I followed the steps and set the the path correctly. this is my environment file


PATH="/usr/lib/jvm/java-6-sun-1.6.0.22/bin:.:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"
JAVA_HOME="/usr/lib/jvm/java-6-sun-1.6.0.22"
CLASSPATH="/usr/lib/jvm/java-6-sun-1.6.0.22/lib:."
but im getting an error when im trying to run a simple java programme even. for example if i run the program using

java testit gives me

Exception in thread "main" java.lang.NoClassDefFoundError: testbut if i run it using

java -classpath . testthen it runs properly. can any one help me with this ? Thanks in advance.

[cwbr]

I'm pretty sure that the problem with that is the ":." at the end of the CLASSPATH. I removed it from mine and everything worked fine.
If anyone wants to tell me why some people have this and do not seem to have a problem, I would be interested to know. Also, what does the ":." addition do?

[r-senior]

You don't need to set JAVA_HOME and CLASSPATH to program in Java.

For example:


$ echo $JAVA_HOME

$ echo $CLASSPATH

$ vi Test.java
$ cat Test.java
public class Test {
public static void main(String ... args) {
System.out.println("Hello World");
}
}
$ javac Test.java
$ java Test
Hello World


Read this carefully to understand why PATH does not need to be set for Java - in fact why it should not be set:


$ which java
/usr/bin/java
$ ls -l /usr/bin/java
lrwxrwxrwx 1 root root 22 2011-04-08 15:30 /usr/bin/java -> /etc/alternatives/java
$ ls -l /etc/alternatives/java
lrwxrwxrwx 1 root root 36 2011-04-08 15:30 /etc/alternatives/java -> /usr/lib/jvm/java-6-sun/jre/bin/java


When it comes to using other libraries, it is much better to specify them on the command line or in a script/build tool rather than in a machine specific configuration. If there are too many, you should be using a build tool like Maven or an IDE (preferably an IDE that supports Maven builds ;)).

If you use an IDE without Maven, .jar files usually get added to the classpath as "libraries" for the project. It's just locating the .jar file and adding that location to the -classpath option.

If you use Maven, Maven takes care of your library dependencies (and their dependencies (and their dependencies ...)).

[ishan_sangai]

hey,

Thanks
It helped me. Now I can see classpath with echo $CLASSPATH.

regards,
Ishan