Table of Contents

• Chapter 1: Introduction to Regular Expressions in Java 1
  • What is a Regular Expression?1
  • Overview of Java Regex API (java.util.regex)2
  • Basic syntax and structure of regex3
  • Your first Java regex program: simple pattern matching example4
Chapter 2: Basic Regex Syntax and Patterns 6
• Literal characters and metacharacters6
• Character classes and predefined character sets8
• Quantifiers: *, +, ?, {n,m}9
• Anchors: ^ and $11
• Simple matching examples12
Chapter 3: Pattern and Matcher Classes 14
• Understanding Pattern and Matcher classes14
• Compiling a regex pattern15
• Matcher methods: matches(), find(), lookingAt()16
• Extracting matches and groups18
• Example: Validate email addresses20
Chapter 4: Grouping and Capturing 22
• Capturing groups and backreferences22
• Non-capturing groups (?:...)24
• Named capturing groups25
• Example: Extracting date components from strings27
Chapter 5: Character Classes and POSIX Character Classes 29
• Custom character classes [abc] and ranges [a-z]29
• Negated classes [^...]30
• POSIX character classes like \p{Lower}, \p{Upper}, etc.32
• Example: Validating password complexity33
Chapter 6: Advanced Quantifiers and Lazy Matching 35
• Greedy vs. reluctant quantifiers35
• Possessive quantifiers37
• Examples demonstrating differences38
• Example: Extracting HTML tags without overmatching40
Chapter 7: Boundary Matchers and Word Boundaries 41
• Word boundaries \b and \B41
• Start/end of input vs line boundaries ^, $, \A, \Z43
• Example: Find whole words only44
Chapter 8: Lookahead and Lookbehind Assertions 46
• Positive lookahead (?=...)46
• Negative lookahead (?!...)48
• Positive lookbehind (?<=...)49
• Negative lookbehind (?<!...)51
• Practical examples: Validate complex password rules, extract context-sensitive patterns52
Chapter 9: Unicode and Internationalization in Regex 55
• Unicode character classes and scripts \p{IsGreek}, etc.55
• Matching emojis and special symbols57
• Handling normalization and diacritics59
• Example: Regex for multilingual text processing61
Chapter 10: Regex Performance and Optimization 63
• Common performance pitfalls63
• Avoiding catastrophic backtracking65
• Using atomic groups and possessive quantifiers for optimization67
• Example: Efficient parsing of large logs69
Chapter 11: Input Validation with Regex 71
• Validating emails, phone numbers, postal codes71
• URL validation73
• Example: Form input validation in Java applications75
Chapter 12: Text Searching and Extraction 78
• Searching multiple occurrences78
• Extracting structured data from logs and reports80
• Example: Extract IP addresses from log files81
Chapter 13: Data Cleaning and Transformation 84
• Removing unwanted characters84
• Replacing patterns using replaceAll and replaceFirst86
• Example: Normalize phone numbers or dates88
Chapter 14: Parsing and Tokenizing with Regex 91
• Splitting strings by patterns91
• Tokenizing input for simple parsing93
• Example: Parsing CSV or custom delimited data95
Chapter 15: Regex Debugging and Testing Tools 97
• Using online regex testers and Java IDE regex support97
• Writing test cases for regex patterns99
• Best practices for maintainable regex code102
Chapter 16: Integrating Regex with Java Streams and Lambdas 103
• Using regex with Stream API103
• Filtering and mapping with regex matches105
• Example: Processing large datasets with regex and streams108
Chapter 17: Appendices 110
• Regex Syntax Quick Reference111
• Java Regex API Summary113
• Common Regex Patterns Library114
• Glossary of Terms116