This method appends or adds one or more strings to an existing StringSet-class.
这种方法添加或添加一个或多个字符串,以现有的StringSet-class。
方法----------Methods----------
This method is for appending strings to a StringSet-class object after it has been constructed.
此方法适用于已建成后追加字符串StringSet-class对象的。
the first argument is the StringSet-class object to which the values are to be added, and the second is the strings that are being added.
第一个参数是StringSet-class对象的值是要添加,二是正在添加的字符串。