Question

I am trying to create .jar files in java which can be used by including it in other projects. It doesn’t contain any main but only classes and methods. I am using th following command to create .jar file from command line

jar cf firstjar.jar *

I am including the jar file in my project but still the class is not available in the project.
What’s the problem in this.

Answer 1

My guess is that you’ve got a problem with the directory structure.

Suppose you have a class like this:

package org.foo;

public class Bar {}

There should be Bar.class flie in a directory org/foo. That structure has to be in the jar file as well – so you should go to the directory containing org and run:

jar cf firstjar.jar org

(Or whatever your top-level package name is.)

If you just include the classfiles from the foo directory then Java’s expectations of where to find things will be invalid.