code: public int fringesOn (int first, int second)
      {
          FringeRecord f1 = _frecs.get(first);
  
          // we better have a fringe record for the first
          if (null != f1) {
  
              // it had better have some tilesets defined
              if (f1.tilesets.size() > 0) {
  
                  FringeRecord f2 = _frecs.get(second);
  
                  // and we only fringe if second doesn't exist or has a lower
                  // priority
                  if ((null == f2) || (f1.priority > f2.priority)) {
                      return f1.priority;
                  }
              }
          }
  
          return -1;
      }
docs: If the first base tileset fringes upon the second, return the
  fringe priority of the first base tileset, otherwise return -1.