Book Image

Java 9 Regular Expressions

By : Anubhava Srivastava
Book Image

Java 9 Regular Expressions

By: Anubhava Srivastava

Overview of this book

Regular expressions are a powerful tool in the programmer's toolbox and allow pattern matching. They are also used for manipulating text and data. This book will provide you with the know-how (and practical examples) to solve real-world problems using regex in Java. You will begin by discovering what regular expressions are and how they work with Java. This easy-to-follow guide is a great place from which to familiarize yourself with the core concepts of regular expressions and to master its implementation with the features of Java 9. You will learn how to match, extract, and transform text by matching specific words, characters, and patterns. You will learn when and where to apply the methods for finding patterns in digits, letters, Unicode characters, and string literals. Going forward, you will learn to use zero-length assertions and lookarounds, parsing the source code, and processing the log files. Finally, you will master tips, tricks, and best practices in regex with Java.
Table of Contents (15 chapters)
Title page
About the Author
About the Reviewer
Customer Feedback
Free Chapter
Getting Started with Regular Expressions

Capturing groups

Groups are a very useful feature of regular expressions, which are supported in all the flavors of regular expressions. Groups are used to combine multiple characters or multiple smaller components of regular expressions into a single unit. We create groups by placing a series of characters or subpatterns inside round brackets or parentheses, ( and ). For example, consider the following regex pattern:


It means a capturing group that uses alternation. It either matches the letters b, l, u, and e or it matches the letters r, e, and d. In other words, it matches the strings blue or red, and more importantly, it creates a capturing group with either of the two matched strings. Each group becomes a single unit that can be used to apply certain constructs to the entire group. For example, anchors, boundary assertion, quantifiers, or alternation can be restricted to a part of the regular expression represented by the group. For example, look at the following regex...