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.