code: public Object remove (int key)
      {
          int size = _keys.length, start = key % size;
          for (int ii = 0; ii < size; ii++) {
              int idx = (ii + start) % size;
              if (_keys[idx] == key) {
                  Object value = _values[idx];
                  _keys[idx] = -1;
                  _values[idx] = null;
                  return value;
              }
          }
          return null;
      }
docs: Removes the mapping associated with the specified key. The previous
  value of the mapping will be returned.