Import package does not work - beginner help

Question

Hi, I'm a beginner with java. I just trying to figure out how to use packages. I followed everything in the tutorial, but I can't figure out why my simple example does not work.
I made the following directories three, for the sake of the example.
in /home/username/Desktop I created a directory named it
inside it I created prove
inside prove I created test1 and test2
Inside test1 I created the following sample class:
package it.prove.test1;
public class HelloWorld
     private String message;
     public HelloWorld(String message)
          this.message = message;
     public String getMessage()
          return this.message;
}in the directory test2 I created this other one:
package it.prove.test2;
import it.prove.test1.HelloWorld;
public class HelloWorldProgram
     public static void main(String[] args)
          HelloWorld hw = new HelloWorld("Guten Tag, Welt!");
          System.out.println(hw.getMessage());
}So now I have this three:
it
it/prove
it/prove/test1, it/prove/test2
As I said in test1 there is HelloWorld.java and in test2 HelloWorldProgram.java.
When I compile HelloWorld.java, it worked fine.
When I try to compile HelloWorldProgram.java, the compiler says that cannot find package it.prove.test1..
Why that? What did I make wrong?
Sorry both for my bad english (it is not my first language) and for the really trivial question (I'm a really beginner).
Tnx to whoever will help

Answer 1

Assuming you are running on Windows here.
Packages are directly tied to the classpath. Before java can find the it.prove.test1 package, it needs to be a part of the classpath. To make this possible, you need to add the root of the path, where the 'it' directory is in, to the classpath, like this:
javac -cp .;/home/username/Desktop file.java
the -cp switch tells java which classpath to use; it consists of two elements:
. = current directory
/home/username/Desktop = the directory containing the 'it' package root
When run like this, it should work. The same goes for running the code, you would run it like this:
java -cp .;/home/username/Desktop it.prove.test2.HelloWorldProgram
Hope that gives you the hints you need.