Chapter 1, Getting Started with Regular Expressions, teaches what regular expressions are, what problems are best solved using regular expressions, and the rules to follow while writing them.

Chapter 2, Understanding the Core Constructs of Java Regular Expressions, covers quantifiers, anchors, boundary matchers, and all the available character classes and properties in Java. We will also learn Unicode text matching using regex in Java.

Chapter 3, Working with Groups, Capturing, and References, explores how to match and capture text in regex, the various types of groups available to us, the naming and numbering of a captured group, and how we should use back-reference for the captured groups.

Chapter 4, Regular Expression Programming Using Java String and Scanner APIs, introduces Java regex using Java String methods, and we will move on to regex capabilities in the Java Scanner API.

Chapter 5, Introduction to Java Regular Expression APIs - Pattern and Matcher Classes, discusses the dedicated Java APIs, java.util.regex.Pattern and java.util.regex.Matcher, for complete regex capabilities.

Chapter 6, Exploring Zero-width Assertions, Lookarounds, and Atomic Groups, focuses on zero-width assertions in regex. The chapter covers various zero-width assertions and their usages. We will then move on to learn the important topic of lookarounds in regex.

Chapter 7, Understanding the Union, Intersection, and Subtraction of Character Classes, says that the Java language has added the features of using the intersection and union of character classes in regex. This chapter covers these features.

Chapter 8, Regular Expression Pitfalls, Optimization, and Performance Improvements, explains how to test and optimize a poorly performing regex and various other performance tips.

The software in this book was tested on Java version 9 on Ubuntu version 16.10. However, all the examples can also be run on the Windows and macOS X operating systems.

This book is for Java developers who would like to understand and use regular expressions. If you are dealing with text processing problems, such as text validation, searching, and text manipulation, then learning regex is very important for you to make your job easier. This book does not expect readers to have any prior regex knowledge, since the book will cover every aspect of regex, starting from the absolute basics of regex. However, a basic knowledge of Java is assumed in order to be able to write and execute the example programs provided in the book.

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The next lines of code read the link and assign it to the to the BeautifulSoup function."

A block of code is set as follows:

package example.regex;
public class StringMatches 
{ 
  public static void main(String[] args) 
}

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

[default]
exten => s,1,Dial(Zap/1|30)
exten => s,2,Voicemail(u100) 
exten => s,102,Voicemail(b100) 
exten => i,1,Voicemail(s0)

Any command-line input or output is written as follows:

C:\Python34\Scripts> pip install -upgrade pipC:\Python34\Scripts> pip install pandas

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "In order to download new modules, we will go to Files | Settings | Project Name | Project Interpreter."

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