code: @Nullable
    public String setProperty (final String sKey, final String sValue)
    {
      return put (sKey, sValue);
    }
docs: Calls the <tt>Hashtable</tt> method <code>put</code>. Provided for
  parallelism with the <tt>getProperty</tt> method. Enforces use of strings
  for property keys and values. The value returned is the result of the
  <tt>Hashtable</tt> call to <code>put</code>.
  
  @param sKey
  the key to be placed into this property list.
  @param sValue
  the value corresponding to <tt>key</tt>.
  @return the previous value of the specified key in this property list, or
  <code>null</code> if it did not have one.
  @see #getProperty
  @since 1.2