code: protected void invokeFaxJobIDValidation(FaxJob faxJob)
      {
          //validate fax job is not null
          this.invokeFaxJobNullValidation(faxJob);
  
          //validate fax job ID
          String faxJobID=faxJob.getID();
          if((faxJobID==null)||(faxJobID.length()==0))
          {
              throw new FaxException("Fax job ID not provided.");
          }
      }
docs: This function invokes the fax job null validation.
  
  @param   faxJob
  The fax job