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Trail: Bonus
Lesson: Regular Expressions

Introduction

What are regular expressions?

Regular expressions are a way to describe a set of strings based on common characteristics shared by each string in the set. They can be used as a tool to search, edit or manipulate text or data. You must learn a specific syntax to create regular expressions--one that goes beyond the normal syntax of the JavaTM programming language. Regular expressions range from being simple to quite complex, but once you understand the basics of how they're constructed, you'll be able to understand any regular expression.

This tutorial will teach you the regular expression syntax supported by the java.util.regex(in the API reference documentation) API, and will present plenty of working examples to illustrate how the various objects interact. In the world of regular expressions, there are many different flavors to choose from, such as grep, Perl, Tcl, Python, PHP, and awk. The regular expressions in the java.util.regex API are most similar to Perl.

How are regular expressions represented in this package?

The java.util.regex package consists of three classes: Pattern(in the API reference documentation), Matcher(in the API reference documentation), and PatternSyntaxException(in the API reference documentation).

In the last few sections in this lesson, we'll explore each class in detail with a separate section devoted to each class. But first, let's learn the details of how regular expressions are created. The next section introduces a simple test harness that we'll use repeatedly to explore how regular expressions are constructed.


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