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Java 9 Regular Expressions

By : Anubhava Srivastava

5 (2)

Buy this Book

Java 9 Regular Expressions

5 (2)

By: Anubhava Srivastava

Buy this Book

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.

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

Getting Started with Regular Expressions

Introduction to regular expressions

Summary

Understanding the Core Constructs of Java Regular Expressions

Understanding the core constructs of regular expressions

Quantifiers

Summary

Working with Groups, Capturing, and References

Capturing groups

Non-capturing groups

Back references

Summary

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

Introduction to Java Regular Expression APIs - Pattern and Matcher Classes

The MatchResult interface

The Pattern class

The Matcher class

Summary

Exploring Zero-Width Assertions, Lookarounds, and Atomic Groups

Zero-width assertions

\G boundary assertion

Atomic groups

Lookahead assertions

Lookbehind assertions

Summary

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

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

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Using regular expressions in Java Scanner API

A scanner is a utility class used for parsing the input text and breaking the input into tokens of various types, such as Boolean, int, float, double, long, and so on. It generates tokens of various types using regular expression-based delimiters. The default delimiter is a whitespace. Using the Scanner API, we can generate tokens of all the primitive types in addition to string tokens.

The String, Pattern, and Matcher classes are able to parse the input and generate tokens of the String type only, but the Scanner class is very useful for checking and generating tokens of different types from the input source. The Scanner instance can be constructed using the File, InputStream, Path, Readable, ReadableByteChannel, and String arguments.