code: public final String[] keys()
    {
      String [] keysArr = new String[m_firstFree];
  
      for (int i = 0; i < m_firstFree; i++)
      {
        keysArr[i] = m_map[i];
      }
  
      return keysArr;
    }
docs: Return array of keys in the table.
  
  @return Array of strings