The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases.
Now that you've completed this lesson on regular expressions, you'll probably find that your main references will be the API documentation for the following classes:
Pattern,
Matcher, and
PatternSyntaxException.
For a more precise description of the behavior of regular expression constructs, we recommend reading the book Mastering Regular Expressions by Jeffrey E. F. Friedl.