Name: Java 9 Regular Expressions
Author: Anubhava Srivastava
ISBN: 9781787288034

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Java 9 Regular Expressions

Anubhava Srivastava

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coverpage
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Title page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Why subscribe?
Customer Feedback
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Downloading the example code
Errata
Piracy
Questions
Getting Started with Regular Expressions
Introduction to regular expressions
A bit of history of regular expressions
Various flavors of regular expressions
What type of problems need regular expressions to solve
The basic rules of regular expressions
Constructs of the standard regular expression and meta characters
Some basic regular expression examples
Eager matching
The effect of eager matching on regular expression alternation
Summary
Understanding the Core Constructs of Java Regular Expressions
Understanding the core constructs of regular expressions
Quantifiers
Basic quantifiers
Examples using quantifiers
Greedy versus reluctant (lazy) matching using quantifiers
Possessive quantifiers
Boundary constructs
Examples using boundary constructs
Character classes
Examples of character classes
Range inside a character class
Examples of character range
Escaping special regex metacharacters and escaping rules inside the character classes
Escaping inside a character class
Examples of escaping rules inside the character class
Literally matching a string that may contain special regex metacharacters
Negated character classes
Examples of negated character classes
Predefined shorthand character classes
POSIX character classes
Unicode support in Java regular expressions
Commonly used Unicode character properties
Negation of the preceding regex directives
Unicode scripts support
Examples of matching Unicode text in regular expressions
Double escaping in a Java String when defining regular expressions
Embedded regular expression mode modifiers
The placement of embedded modes in a Java regular expression
Disabling mode modifiers
Summary
Working with Groups, Capturing, and References
Capturing groups
Group numbering
Named groups
Non-capturing groups
Advantages of non-capturing groups
Back references
Back reference of a named group
Replacement reference of a named group
Forward references
Invalid (non-existing) backward or forward references
Summary
Regular Expression Programming Using Java String and Scanner APIs
Introduction to the Java String API for regular expressions evaluation
Method - boolean matches(String regex)
Example of the matches method
Method - String replaceAll(String regex, String replacement)
Examples of the replaceAll method
Method - String replaceFirst(String regex, String replacement)
Examples of the replaceFirst method
Methods - String split methods
The limit parameter rules
Examples of the split method
Example of the split method using the limit parameter
Using regular expressions in Java Scanner API
Summary
Introduction to Java Regular Expression APIs - Pattern and Matcher Classes
The MatchResult interface
The Pattern class
Examples using the Pattern class
Filtering a list of tokens using the asPredicate() method
The Matcher class
Examples using the Matcher class
Method Boolean lookingAt()
The matches() method
The find() and find(int start) methods
The appendReplacement(StringBuffer sb, String replacement) method
The appendTail(StringBuffer sb) method
Example of the appendReplacement and appendTail methods
Summary
Exploring Zero-Width Assertions, Lookarounds, and Atomic Groups
Zero-width assertions
Predefined zero-width assertions
Regex defined zero-width assertions
G boundary assertion
Atomic groups
Lookahead assertions
Positive lookahead
Negative lookahead
Lookbehind assertions
Positive lookbehind
Negative lookbehind
Capturing text from overlapping matches
Be careful with capturing groups inside a lookahead or lookbehind atomic group
Lookbehind limitations in Java regular expressions
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
Do not forget to escape regex metacharacters outside a character class
Avoid escaping every non-word character
Avoid unnecessary capturing groups to reduce memory consumption
However, don t forget to use the required group around alternation
Use predefined character classes instead of longer versions
Use the limiting quantifier instead of repeating a character or pattern multiple times
Do not use an unescaped hyphen in the middle of a character class
The mistake of calling matcher.goup() without a prior call to matcher.find(), matcher.matches(), or matcher.lookingAt()
Do not use regular expressions to parse XML / HTML data
How to test and benchmark your regular expression performance
Catastrophic or exponential backtracking
How to avoid catastrophic backtracking
Optimization and performance enhancement tips
Use a compiled form of regular expressions
Use a negated character class instead of the greedy and slow .* or .+
Avoid unnecessary grouping
Use lazy quantifiers strategically instead of greedy quantifiers that cause excessive backtracking
Make use of possessive quantifiers to avoid backtracking
Extract common repeating substrings out of alternation
Use atomic group to avoid backtracking and fail fast
Summary

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Java 9 Regular Expressions