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Understanding the Core Constructs of Java Regular Expressions

Using Java as a regular expression flavor, in this chapter, we will go a bit deeper and learn in detail about anchors, quantifiers, boundary matchers, all the available character classes, negated character classes, predefined character classes, and character classes escaping rules, using Java as a reference point. You will also learn Unicode text matching, using regular expressions in Java. We will also cover greedy versus non-greedy (lazy matching) and the change of regular expression behavior with lazy matching.

We will cover the following topics in this chapter:

Anchors and quantifiers
Boundary matchers
Character classes
Regex escaping rules
Escaping inside character classes
Negated character classes
Predefined character classes
Unicode characters matching
Greedy quantifiers
Lazy quantifiers
Possessive quantifiers...

Key benefits

Discover regular expressions and how they work

Implement regular expressions with Java to your code base

Learn to use regular expressions in emails, URLs, paths, and IP addresses

Description

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.

What you will learn

Understand the semantics, rules, and core concepts of writing Java code involving regular expressions

Learn about the java.util.Regex package using the Pattern class, Matcher class, code snippets, and more

Match and capture text in regex and use back-references to the captured groups

Explore Regex using Java String methods and regex capabilities in the Java Scanner API

Use zero-width assertions and lookarounds in regex

Test and optimize a poorly performing regex and various other performance tips

What do you get with Print?

Instant access to your digital eBook copy whilst your Print order is Shipped

Paperback book shipped to your preferred address

Download this book in EPUB and PDF formats

Access this title in our online reader with advanced features

DRM FREE - Read whenever, wherever and however you want

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Amazon Customer Jun 08, 2018

This book is enough to have an in depth knowledge in Regular expressions.

Amazon Verified review

Justin Apr 19, 2018

Amazingly insightful, here is a man that really knows his stuff and will help you figure out the most in depth problems. I would recommend this to anyone who actually wants to know how to solve problems with regex.

Special Character	Meaning
\0c	A character with the octal value c
\0cc	A character with the octal value cc
\0ncc	A character with the octal value ncc, where n cannot be more than 3
\xhh	A character with the hexadecimal value 0xhh
\uhhhh	A character with the hexadecimal value 0xhhhh
\x{h...h}	A character with the hexadecimal value 0xh...h, where h must be a valid CODE_POINT
\n	Newline character or `u000A`
\t	Tab character or `u0009`
\r	Carriage return character or `u000D`
\f	Form feed character or `u000C`
\e	Escape character or `u\u001B`
\a	Bell character or `\u0007`
\cn	A control character represented by n

Quantifier	Meaning
m*	Match m zero or more times
m+	Match m one or more times
m?	Match m one or zero times (also called an optional match)
m{X}	Match m exactly X times
m{X,}	Match m X or more times
m{X,Y}	Match m at least X and at most Y times

Java 9 Regular Expressions: A hands-on guide to implement zero-length assertions, back-references, quantifiers, and many more

What do you get with Print?

Java 9 Regular Expressions

Understanding the Core Constructs of Java Regular Expressions

Understanding the core constructs of regular expressions

Quantifiers

Basic quantifiers

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Java 9 Regular Expressions: A hands-on guide to implement zero-length assertions, back-references, quantifiers, and many more

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