What happens next in this paragraph?

How to encode a string to base64 with java
Enter info and name file
Start up your editor, such as notepad or vi, and enter the preliminaries, such as the class declaration and known constants.
Name the file base64.java.
Those constant values are specified, so the article states, in the relevant rfcs.
It is generally a good idea read all relevant rfcs before beginning coding. Treating characters as bytes means that multibyte characters, such as japanese or chinese, will not be correctly encoded.