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.

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Table of Contents (15 chapters)
Title page
Title page
Credits
Credits
About the Author
About the Author
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Customer Feedback
Customer Feedback
Preface
Preface
Free Chapter
1
Getting Started with Regular Expressions
Getting Started with Regular Expressions
Introduction to regular expressions
Summary
2
Understanding the Core Constructs of Java Regular Expressions
Understanding the Core Constructs of Java Regular Expressions
Understanding the core constructs of regular expressions
Quantifiers
Summary
3
Working with Groups, Capturing, and References
Working with Groups, Capturing, and References
Capturing groups
Non-capturing groups
Back references
Summary
4
Regular Expression Programming Using Java String and Scanner APIs
Regular Expression Programming Using Java String and Scanner APIs
Introduction to the Java String API for regular expressions' evaluation
Using regular expressions in Java Scanner API
Summary
5
Introduction to Java Regular Expression APIs - Pattern and Matcher Classes
Introduction to Java Regular Expression APIs - Pattern and Matcher Classes
The MatchResult interface
The Pattern class
The Matcher class
Summary
6
Exploring Zero-Width Assertions, Lookarounds, and Atomic Groups
Exploring Zero-Width Assertions, Lookarounds, and Atomic Groups
Zero-width assertions
\G boundary assertion
Atomic groups
Lookahead assertions
Lookbehind assertions
Summary
7
Understanding the Union, Intersection, and Subtraction of Character Classes
Understanding the Union, Intersection, and Subtraction of Character Classes
The union of character classes
The intersection of character classes
The subtraction of character classes
Why should you use composite character classes?
Summary
8
Regular Expression Pitfalls, Optimization, and Performance Improvements
Regular Expression Pitfalls, Optimization, and Performance Improvements
Common pitfalls and ways to avoid them while writing regular expressions
How to test and benchmark your regular expression performance
Catastrophic or exponential backtracking
Optimization and performance enhancement tips
Summary

Introduction to the Java String API for regular expressions' evaluation

The Java String API provides some useful methods to evaluate regular expressions against a text represented by the String object. Let's list those methods from the String class:

Method Signature

Purpose

boolean matches(String regex)

Matches the given regular expression against the string that the method is invoked on and returns true/false, indicating whether the match is successful (true) or not (false).

String replaceAll(String regex, String replacement)

Replaces each substring of the subject string that matches the given regular expression with the replacement string and returns the new string with the replaced content.

String replaceFirst(String regex, String replacement)

This method does the same as the previous one with the exception that it replaces only the first substring of the subject string that matches the given regular expression with the replacement string and returns the new string with the replaced content.

String...

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