Using JDK 1.4

Folks would be great if you could help me out here :

Lets say I have a file called Sample1.java under

<directory>/a/b :

The file Sample1.java is as follows :
package a.b;
public class Sample1
{
       public Sample1()
       {

       }

   public static void main(String []args)
   {
       Sample a =new Sample();
       System.out.println("hello world");
   }
}

and under <directory>
I have got a class.jar that contains just Sample.class ( no package or
anything,just the class file)

How do I compile this??
I do the following:
<directory>/a/b/javac -classpath .:<directory>/class.jar Sample1.java

I get the following error:
--------------------------------------------------------------
Sample1.java:12: cannot resolve symbol
symbol  : class Sample
location: class a.b.Sample1
       Sample a =new Sample();
       ^
Sample1.java:12: cannot resolve symbol
symbol  : class Sample
location: class a.b.Sample1
       Sample a =new Sample();
--------------------------------------------------------------

How do I resolve this issue?What am I doing wrong here.
Please dont ask me to put the Sample.class in a package , I wont be
able to do that since that jar is actually already available.