code: @Nullable
    public String getProperty (@Nullable final String sKey)
    {
      final String sValue = super.get (sKey);
      return sValue == null && m_aDefaults != null ? m_aDefaults.getProperty (sKey) : sValue;
    }
docs: Searches for the property with the specified key in this property list. If
  the key is not found in this property list, the default property list, and
  its defaults, recursively, are then checked. The method returns
  <code>null</code> if the property is not found.
  
  @param sKey
  the property key.
  @return the value in this property list with the specified key value.
  @see #setProperty