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Java 9 Regular Expressions

You're reading from   Java 9 Regular Expressions A hands-on guide to implement zero-length assertions, back-references, quantifiers, and many more

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Product type Paperback
Published in Jul 2017
Publisher Packt
ISBN-13 9781787288706
Length 158 pages
Edition 1st Edition
Languages
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Author (1):
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Anubhava Srivastava Anubhava Srivastava
Author Profile Icon Anubhava Srivastava
Anubhava Srivastava
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Table of Contents (9) Chapters Close

Preface 1. Getting Started with Regular Expressions 2. Understanding the Core Constructs of Java Regular Expressions FREE CHAPTER 3. Working with Groups, Capturing, and References 4. Regular Expression Programming Using Java String and Scanner APIs 5. Introduction to Java Regular Expression APIs - Pattern and Matcher Classes 6. Exploring Zero-Width Assertions, Lookarounds, and Atomic Groups 7. Understanding the Union, Intersection, and Subtraction of Character Classes 8. Regular Expression Pitfalls, Optimization, and Performance Improvements

Common pitfalls and ways to avoid them while writing regular expressions


Let's discuss some common mistakes people make while building regular expressions to solve various problems.

Do not forget to escape regex metacharacters outside a character class

You learned that all the special metacharacters, such as *, +, ?, ., |, (, ), [, {, ^, $, and so on, need to be escaped if the intent is to match them literally. I often see cases where programmers leave them unescaped, thus giving a totally different meaning to the regular expression. The Java regex API that we discussed in Chapter 5, Introduction to Java Regular Expressions APIs - Pattern and Matcher Classes, throws a non-checked exception if a regex pattern is wrongly formatted and cannot be compiled.

Avoid escaping every non-word character

Some programmers overdo escaping, thinking that they need to escape every non-word character such as colon, hyphen, semicolon, forward slash, and whitespace, which is not correct. They end up writing a regular...

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