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Module 06: Strings

Overview

This module provides comprehensive coverage of String handling in Java, including String class, StringBuilder, StringBuffer, string manipulation, pattern matching, and regular expressions.

Learning Objectives

  • Understand String immutability and memory management
  • Master String class methods
  • Work with StringBuilder and StringBuffer
  • Perform string manipulation and formatting
  • Learn regular expressions
  • Understand String pool concept

Topics Covered

6.1 Introduction to Strings

  • What are Strings?
  • String as Character Array
  • Strings as Objects
  • String Literals
  • String Immutability
  • Why Strings are Immutable

6.2 Creating Strings

6.2.1 String Literals

  • String Literal Syntax
  • String Pool (String Constant Pool)
  • Literal vs Object Creation
  • Interning Strings

6.2.2 Using new Keyword

  • Creating String Objects
  • Memory Allocation
  • Heap vs String Pool

6.2.3 Character Arrays to String

  • char[] to String
  • Converting Back to char[]

6.2.4 String Constructor Methods

  • String()
  • String(char[])
  • String(byte[])
  • String(StringBuilder)
  • String(StringBuffer)

6.3 String Class Methods

6.3.1 Length and Character Access

  • length()
  • charAt(int index)
  • getChars()
  • toCharArray()
  • codePointAt()
  • codePointCount()

6.3.2 String Comparison

  • equals()
  • equalsIgnoreCase()
  • compareTo()
  • compareToIgnoreCase()
  • contentEquals()
  • == vs equals()

6.3.3 String Searching

  • indexOf()
  • lastIndexOf()
  • contains()
  • startsWith()
  • endsWith()
  • matches()

6.3.4 String Extraction

  • substring(int beginIndex)
  • substring(int beginIndex, int endIndex)
  • subSequence()
  • split()
  • split() with limit

6.3.5 String Modification

  • concat()
  • replace()
  • replaceAll()
  • replaceFirst()
  • toLowerCase()
  • toUpperCase()
  • trim()
  • strip() (Java 11+)
  • stripLeading() (Java 11+)
  • stripTrailing() (Java 11+)

6.3.6 String Conversion

  • valueOf() methods
  • toString()
  • format()
  • formatted() (Java 15+)

6.3.7 String Checking

  • isEmpty()
  • isBlank() (Java 11+)
  • startsWith()
  • endsWith()
  • contains()

6.4 String Pool and Memory

  • String Pool Concept
  • How String Pool Works
  • intern() Method
  • Memory Optimization
  • Garbage Collection

6.5 StringBuilder Class

6.5.1 Introduction to StringBuilder

  • Mutable Strings
  • When to Use StringBuilder
  • StringBuilder vs String

6.5.2 StringBuilder Methods

  • append()
  • insert()
  • delete()
  • deleteCharAt()
  • replace()
  • reverse()
  • capacity()
  • ensureCapacity()
  • setLength()
  • toString()

6.5.3 StringBuilder Performance

  • Amortized Time Complexity
  • Memory Allocation
  • Capacity Management

6.6 StringBuffer Class

6.6.1 Introduction to StringBuffer

  • Thread-Safe Mutable Strings
  • Synchronized Methods
  • When to Use StringBuffer

6.6.2 StringBuffer Methods

  • Same as StringBuilder
  • Thread Safety Overhead

6.6.3 StringBuilder vs StringBuffer

  • Performance Comparison
  • Thread Safety
  • Use Case Scenarios

6.7 String Formatting

6.7.1 printf() Method

  • Format Specifiers
  • Formatting Numbers
  • Formatting Dates
  • Alignment and Padding

6.7.2 String.format()

  • Creating Formatted Strings
  • Format Specifiers
  • Locale-Specific Formatting

6.7.3 Text Blocks (Java 15+)

  • Multi-line String Literals
  • Syntax and Usage
  • Indentation Control
  • Escape Sequences

6.8 Regular Expressions

6.8.1 Introduction to Regex

  • Pattern Matching
  • Regex Syntax
  • Meta Characters
  • Character Classes

6.8.2 Pattern Class

  • compile()
  • matcher()
  • matches()
  • split()
  • quote()

6.8.3 Matcher Class

  • find()
  • matches()
  • lookingAt()
  • group()
  • start() and end()
  • replaceAll()
  • replaceFirst()

6.8.4 Common Regex Patterns

  • Email Validation
  • Phone Number Validation
  • URL Validation
  • Password Validation
  • Date Format Validation
  • IP Address Validation

6.9 String Algorithms

6.9.1 String Manipulation

  • Reversing Strings
  • Palindrome Check
  • Anagram Check
  • String Rotation
  • Character Frequency
  • Remove Duplicates

6.9.2 String Searching

  • KMP Algorithm
  • Rabin-Karp Algorithm
  • Boyer-Moore Algorithm
  • Z Algorithm

6.9.3 String Matching

  • Substring Search
  • Pattern Matching
  • Wildcard Matching
  • Regular Expression Matching

6.10 String Tokenization

  • StringTokenizer Class
  • split() Method
  • Scanner Class
  • Delimiter-Based Splitting

6.11 Character Class

  • Character Wrapper Class
  • isDigit()
  • isLetter()
  • isWhitespace()
  • isUpperCase()
  • isLowerCase()
  • toUpperCase()
  • toLowerCase()

6.12 String Joiner (Java 8+)

  • StringJoiner Class
  • Joining Strings with Delimiter
  • Prefix and Suffix
  • String.join() Method

6.13 String Performance

  • String Concatenation Performance
  • Using + Operator
  • Using concat()
  • Using StringBuilder
  • Compiler Optimizations
  • Best Practices

6.14 String Encoding

  • Character Encoding
  • UTF-8, UTF-16
  • getBytes()
  • Charset Class
  • Encoding and Decoding

6.15 Common String Operations

  • Trimming Whitespace
  • Padding Strings
  • Case Conversion
  • Replacing Characters
  • Removing Characters
  • Counting Occurrences

Hands-on Exercises

  1. Implement string comparison programs
  2. Create palindrome checker
  3. Implement anagram solver
  4. Build string reversal programs
  5. Create regex validators
  6. Implement string searching algorithms
  7. Build text processing applications
  8. Create string formatting examples
  9. Implement word frequency counter
  10. Build password validator
  11. Create text analyzer
  12. Implement string compression

Key Takeaways

  • Strings are immutable in Java
  • String pool optimizes memory
  • StringBuilder for mutable strings
  • StringBuffer for thread-safe operations
  • Regular expressions for pattern matching
  • Proper string handling improves performance

Common Mistakes to Avoid

  • Using + in loops for concatenation
  • Comparing strings with ==
  • Not handling null strings
  • Ignoring case in comparisons
  • Inefficient string building
  • Regex performance issues

Real-World Applications

  • Text processing
  • Data validation
  • Log parsing
  • File processing
  • Web scraping
  • Search functionality
  • Data formatting

Additional Resources

  • String Class Documentation
  • Pattern Class Documentation
  • Regular Expressions Tutorial
  • Effective Java - String Best Practices
  • Unicode Standards

Assessment

  • Quiz on String concepts
  • Practical: String manipulation programs
  • Regex pattern matching exercises
  • Performance optimization challenges
  • Debug string-related errors

Previous Module

Module 05: Arrays

Next Module

Module 07: Object-Oriented Programming