CLASSPATH variable

[stmfc]

i dont have any environment variable CLASSPATH on my PC,
but i can write some java programs via eclipse and run them.
what is the story? do not i need to have CLASSPATH variable in my environment?

[mattmao]

Eclipse is an IDE, so it automatically creates a proper CLASSPATH for your Java classes behind the scenes. You don't have to worry about this.

But if you want to manually specify the CLASSPATH, google for the tutorials. This is fundamental so you would find hundreds of pages about it:)

[JosAH]

do not i need to have CLASSPATH variable in my environment?

Not only don't you need it, you shouldn't want it either. Either pass the classpath
value on the command line when you start the jvm or let your IDE deal with those
nasty little details.

kind regards,

Jos

[stmfc]

Not only don't you need it, you shouldn't want it either. Either pass the classpath
value on the command line when you start the jvm or let your IDE deal with those
nasty little details.

kind regards,

Jos

in a SCJD exam tutorial i see a warning like this:
"When using an IDE (or not, but there’s more of a danger when using an IDE) you can end up being sheltered and protected from things like classpath issues, which allow your program to run fine on your machine and then blow up (OK, just fail to run) at runtime on another system."

thats why i am confused, and why i want to learn how to set CLASSPATH variable, or at least learn how to write portable programs without worrying about CLASSPATH setting.

thanks in advance...

[JosAH]

When you package your application in one or more .jar files you normally set
the classpath values in the .jar manifest file but you never want that variable to
be set in your environment.

For unpackaged applications you can pass that classpath variable on the
command line when you start your virtual machine.

kind regards,

Jos

[stmfc]

When you package your application in one or more .jar files you normally set
the classpath values in the .jar manifest file but you never want that variable to
be set in your environment.

For unpackaged applications you can pass that classpath variable on the
command line when you start your virtual machine.

kind regards,

Jos

Hi JosAH,
unfortunately i am still unclear with this CLASSPATH issue.
in a tutorial explaining Jakarta's POI project i saw an explanation as follows:

Installing HSSF
Go to the Jakarta.apache. org/poi site and download the latest binary for the POI project. Install it anywhere in your system. POI uses Jakarta's commons-logging package. The download includes with the Jakarta-commons.jar file and you must have that path in your classpath to run POI based applications.

i am using eclipse so what should i do for CLASSPATH?
i am not starting my applications via command-line so i cannot pass the classpath variable, and i am not packing them into a jar file for now.

[Nepomuk]

Hi JosAH,
unfortunately i am still unclear with this CLASSPATH issue.
in a tutorial explaining Jakarta's POI project i saw an explanation as follows:

Installing HSSF
Go to the Jakarta.apache. org/poi site and download the latest binary for the POI project. Install it anywhere in your system. POI uses Jakarta's commons-logging package. The download includes with the Jakarta-commons.jar file and you must have that path in your classpath to run POI based applications.

i am using eclipse so what should i do for CLASSPATH?
i am not starting my applications via command-line so i cannot pass the classpath variable, and i am not packing them into a jar file for now.

You're using eclipse, right? Do the following:

1. Open your project in eclipse
2. Right click on your package in the package explorer
3. Chose "Properties "
4. Chose "Java Build Path"
5. Click on "Add External JARs"
6. Choose the JAR, you want to add (jakarta-commons.jar)
7. Close the Properties Window

That should make Eclipse add that JAR to your classpath.

Greetings,
Nepomuk

[stmfc]

now everything is more clear.
josah, mattmao and nepomuk thank you very much.