code: public int findHighestKey(int max) {
          int highest = Integer.MIN_VALUE;
          int index = index(hash(max));
          final int maxTry = capacity;
          for (int i = 0; i < maxTry; i++) {
              if (!slotIsFree(index)) {
                  int k = keys[index];
                  if (k == max) return max;
                  if (max > k && k > highest) highest = k;
              }
              index = nextIndex(index);
          }
          return highest;
      }
docs: Finds the highest key LE `max`,
  for which there is a value.