Table of Contents

• Chapter 1: Introduction to Functional Programming in Java 1
  • What is Functional Programming?1
  • Benefits and Use Cases2
  • Overview of Functional Programming in Java3
Chapter 2: Java 8 Functional Programming Basics 5
• Lambda Expressions: Syntax and Usage5
• Functional Interfaces: Function, Predicate, Consumer, Supplier6
• Method References and Constructor References8
• Example: Simple Calculator Using Lambdas9
Chapter 3: Working with Functional Interfaces 12
• Creating Custom Functional Interfaces12
• Default and Static Methods in Interfaces14
• Composing Functions and Predicates16
• Example: Filtering and Transforming Collections19
Chapter 4: Using Streams for Data Processing 21
• Introduction to Streams API21
• Creating Streams: from Collections, Arrays, and I/O23
• Intermediate Operations: map, filter, sorted, distinct25
• Terminal Operations: forEach, collect, reduce28
• Example: Processing Employee Data with Streams31
Chapter 5: Advanced Stream Operations 34
• Parallel Streams and Performance34
• Short-circuiting Operations: limit, findFirst, anyMatch36
• FlatMap for Nested Data38
• Example: Processing Nested Collections41
Chapter 6: Optional and Handling Nulls Functionally 46
• Using Optional to Avoid NullPointerExceptions46
• Common Optional Operations48
• Example: Safely Navigating Complex Object Graphs51
Chapter 7: Functional Error Handling 56
• Using Either, Try Patterns (Custom Implementations)56
• Function Composition with Error Handling64
• Example: Validating User Input Functionally68
Chapter 8: Functional Design Patterns 76
• Strategy Pattern with Lambdas76
• Command Pattern using Functional Interfaces81
• Observer Pattern with Functional Callbacks84
• Example: Event Handling in GUI Applications88
Chapter 9: Higher-Order Functions and Currying 90
• Defining and Using Higher-Order Functions90
• Partial Application and Currying in Java92
• Example: Building Reusable Validation Functions94
Chapter 10: Lazy Evaluation and Infinite Streams 97
• Understanding Lazy vs. Eager Evaluation97
• Creating and Using Infinite Streams99
• Example: Generating Fibonacci Numbers Lazily101
Chapter 11: Monads and Functional Data Structures 104
• Understanding Monads in Java Context104
• Using Optional as a Monad106
• Introduction to Functional Collections108
• Example: Chaining Operations Safely with Monads110
Chapter 12: Concurrency and Functional Programming 112
• Using CompletableFuture with Functional Style112
• Parallel Stream Pitfalls and Best Practices115
• Reactive Programming Overview with Functional Concepts117
• Example: Asynchronous Data Fetching118
Chapter 13: Functional Programming in Collections and APIs 121
• Using Streams for Collection Manipulation121
• Functional Interfaces in Java APIs (e.g., Comparator, Runnable)123
• Example: Sorting and Grouping Complex Data125
Chapter 14: Functional Programming in Data Processing 128
• Processing Files and I/O Functionally128
• Parsing and Transforming JSON Data130
• Example: Building a CSV Parser with Streams132
Chapter 15: Building Domain-Specific Languages (DSLs) 135
• What is a DSL?135
• Using Lambdas to Create Fluent APIs137
• Example: Building a Simple Query DSL140
Chapter 16: Testing Functional Code 143
• Unit Testing Lambdas and Functional Interfaces143
• Using Mocks and Stubs in Functional Context146
• Example: Testing Stream Pipelines149
Chapter 17: Appendix 152
• Common Functional Interfaces and Usage Examples152
• Writing Efficient Functional Java Code154
• Common Pitfalls and How to Avoid Them156