public class ErrorCode
{
   public static void main(String[] args)
   {
       if ( areaOfCircle( -4 ) == -1 )
       {
           System.out.println("Error");
       }
   }

   public static double areaOfCircle( double radius )
   {
      if ( radius < 0 )
         return -1;        // Error code
      else
         return 3.1415 * radius * radius;
   }
}