code: protected Record locateRecord (int key)
      {
          int index = Math.abs(key)%_buckets.length;
          for (Record rec = _buckets[index]; rec != null; rec = rec.next) {
              if (rec.key == key) {
                  return rec;
              }
          }
          return null;
      }
docs: Internal method to locate the record for the specified key.