Need help: how to make a package into a jar file?

Question

I tried to make a package into a jar file by using:
jar cf a.jar packagedirectory
But when I import one class of this package in an other application, by using:
javac -cp path\a.jar; app.java
the compliler can not find the calss.
The interesting thing is if I do not put the package into the jar file, it works well.
Here is my sample code under path D:\b\b1
package b1;
public class Son
     int x = 10;
     public Son(){
     public int getX(){
          return x;
and the application code under path d:\b
import b1.Son;
public class Father
     public Father(){
     public static void main(String[] args)
          Son son = new Son();
          System.out.println("Hello World!"+son.getX());
Thanks for any advise.
Xin Cheng

Answer 1

You must make sure that you are in the right directory
when you do your jar command to create the archive.
[home/trejkaz/proj/test/classes]% jar -cf a.jar
path/to/package/*.class
Thank you very much.
Yes, I did as what you said, but it does not work.
Here is what I did:
1. Edit Father.java in D:\b
2. Edit Son.java in D:\b\b1
3. Compile Son.java
4. Complie Father.java
5. Make the a.jar by
command jar cf a.jar D:\b\b1\ (I cheked the content of the a.jar, it seems right.)
a.jar is in directory D:\b
6. Delete Son.class in D:\b\b1
7. Run Father.class by
command: java -classpath D:\b\a.jar; Father
error message is: Exception in thread "main" java.lang.NoClassDefFoundError: b1/Son
at Father.main(Father.java:11)
What is the problem?
Thanks again.