created: 03/02/01; revised 10/28/06, 07/15/07, 02/01/10, 08/10/16
created: 03/02/01; revised 10/28/06, 07/15/07, 02/01/10, 08/10/16
A regular expression is a way of describing a set of strings using a compact notation. As in the previous chapters, a string is a sequence of symbols. For this chapter the symbols are ASCII characters (including punctuation and white space).
Regular expressions are used in many programming languages, text editors, search engines, and web applications to specify text patterns. They are especially useful for dealing with user input. Java has several classes that use regular expressions to simplify pattern matching. These classes are discussed in later chapters.