code: @Override
    public boolean containsKey(Object key)
    {
      if (key == null) {
        return false;
      }
  
      K []keys = _keys;
  
      for (int i = _size - 1 ; i >= 0; i--) {
        K testKey = keys[i];
  
        if (key.equals(testKey)) {
          return true;
        }
      }
  
      return false;
    }
docs: Returns true if the map contains the value.