...

Please read my original message again, carefully.
If there is anything that I did not make clear about
helping the reader, feel free to ask.
...

I do not quite understand what the problem is.  Your
code was almost there.  Here is an example of code
that compiles, and runs..

<sscce>
class ReportObject implements Comparable {

   int positionNumber;

   ReportObject(int positionNumber) {
       this.positionNumber = positionNumber;
   }

   public int compareTo(Object obj){
       ReportObject rObj;
       if(obj instanceof ReportObject ){
           rObj = (ReportObject)obj;

           if(this.positionNumber < rObj.getPositionNumber()){
               return -1;
           }else if(this.positionNumber == rObj.getPositionNumber()){
               return 0;
           }else if(this.positionNumber > rObj.getPositionNumber()){
               return 1;
           }

       }else{
           throw new ClassCastException(this +
               " is not comparable to " + obj );
       }
       return -2;
   }

   public int getPositionNumber() {
       return positionNumber;
   }

   public String toString() {
       return "ReportObject: " + getPositionNumber();
   }

   public static void main(String[] args) {
       ReportObject reportObject1 = new ReportObject(1);
       ReportObject reportObject2 = new ReportObject(2);
       Object object = new Object();

       try {
           System.out.println( reportObject2.compareTo(reportObject1) );
           System.out.println( reportObject1.compareTo(reportObject2) );
           System.out.println( reportObject2.compareTo(reportObject2) );
           System.out.println( reportObject2.compareTo(object) );
       } catch(ClassCastException cce) {
           System.out.println( cce.getMessage() );
       }
   }
}
</sscce>

HTH