A Functional Approach to Java Ben Weidig

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Spis treści książki

• Preface
  • New Hardware Needs a New Way of Thinking
  • Java Can Be Functional, Too
  • Why I Wrote This Book
  • Who Should Read This Book
  • What You Will Learn
  • What about Android?
    • A Functional Approach to Android
  • Navigating This Book
  • Conventions Used in This Book
  • Using Code Examples
  • OReilly Online Learning
  • Acknowledgments
• I. Functional Basics
• 1. An Introduction to Functional Programming
  • What Makes a Language Functional?
  • Functional Programming Concepts
    • Pure Functions and Referential Transparency
    • Immutability
    • Recursion
    • First-Class and Higher-Order Functions
    • Functional Composition
    • Currying
    • Partial Function Application
    • Lazy Evaluation
  • Advantages of Functional Programming
  • Disadvantages of Functional Programming
  • Takeaways
• 2. Functional Java
  • What Are Java Lambdas?
    • Lambda Syntax
    • Functional Interfaces
    • Lambdas and Outside Variables
      • Effectively final
      • Re-finalizing a reference
    • What about Anonymous Classes?
  • Lambdas in Action
    • Creating Lambdas
    • Calling Lambdas
    • Method References
      • Static method references
      • Bound non-static method references
      • Unbound non-static method references
      • Constructor references
  • Functional Programming Concepts in Java
    • Pure Functions and Referential Transparency
    • Immutability
    • First-Class Citizenship
    • Functional Composition
    • Lazy Evaluation
  • Takeaways
• 3. Functional Interfaces of the JDK
  • The Big Four Functional Interface Categories
    • Functions
    • Consumers
    • Suppliers
    • Predicates
  • Why So Many Functional Interface Variants?
    • Function Arity
    • Primitive Types
    • Bridging Functional Interfaces
  • Functional Composition
  • Extending Functional Support
    • Adding Default Methods
    • Implementing Functional Interfaces Explicitly
    • Creating Static Helpers
  • Takeaways
• II. A Functional Approach
• 4. Immutability
  • Mutability and Data Structures in OOP
  • Immutability (Not Only) in FP
  • The State of Java Immutability
    • java.lang.String
    • Immutable Collections
      • Unmodifiable Collections
      • Immutable Collection factory methods
      • Immutable copies
    • Primitives and Primitive Wrappers
    • Immutable Math
    • Java Time API (JSR-310)
    • Enums
    • The final Keyword
    • Records
  • How to Achieve Immutability
  • Common Practices
  • Takeaways
• 5. Working with Records
  • Data Aggregation Types
    • Tuples
    • A Simple POJO
    • From POJO to Immutability
    • From POJO to Record
  • Records to the Rescue
    • Behind the Scenes
    • Record Features
      • Component accessors
      • Canonical, compact, and custom constructors
      • Object identity and description
      • Generics
      • Annotations
      • Reflection
    • Missing Features
      • Additional state
      • Inheritance
      • Component default values and convenience constructors
      • Step-by-step creation
  • Use Cases and Common Practices
    • Record Validation and Data Scrubbing
    • Increasing Immutability
    • Creating Modified Copies
      • Wither methods
      • Builder pattern
      • Tool-assisted builder
    • Records as Local Nominal Tuples
    • Better Optional Data Handling
      • Ensure non-null container
      • Add convenience constructors
    • Serializing Evolving Records
    • Record Pattern Matching (Java 19+)
  • Final Thoughts on Records
  • Takeaways
• 6. Data Processing with Streams
  • Data Processing with Iteration
    • External Iteration
    • Internal Iteration
  • Streams as Functional Data Pipelines
    • Stream Features
      • Lazy evaluation
      • (Mostly) stateless and non-interfering
      • Optimizations included
      • Less boilerplate
      • Non-reusable
      • Primitive streams
      • Easy parallelization
      • (Lack of) Exception handling
    • Spliterator, the Backbone of Streams
  • Building Stream Pipelines
    • Creating a Stream
    • Doing the Work
      • Selecting elements
      • Mapping elements
      • Peeking into a stream
    • Terminating the Stream
      • Reducing elements
      • Aggregating elements with collectors
      • Reducing versus collecting elements
      • Aggregate elements directly
      • Finding and matching elements
      • Consuming elements
    • The Cost of Operations
    • Modifying Stream Behavior
  • To Use a Stream, or Not?
  • Takeaways
• 7. Working with Streams
  • Primitive Streams
  • Iterative Streams
  • Infinite Streams
    • Random Numbers
    • Memory Isnt Infinite
  • From Arrays to Streams and Back
    • Object-Type Arrays
    • Primitive Arrays
  • Low-Level Stream Creation
  • Working with File I/O
    • Reading Directory Contents
    • Depth-First Directory Traversal
    • Searching the Filesystem
    • Reading Files Line-By-Line
    • Caveats of File I/O Streams
      • Explicit closing of the stream
      • Weakly consistent directory content
      • Non-guaranteed element order
  • Dealing with Date and Time
    • Querying Temporal Types
    • LocalDate-Range Streams
  • Measuring Stream Performance with JMH
  • More about Collectors
    • Downstream Collectors
      • Transforming elements
      • Reducing elements
      • Flattening collections
      • Filtering elements
      • Composite collectors
    • Creating Your Own Collector
  • Final Thoughts on (Sequential) Streams
  • Takeaways
• 8. Parallel Data Processing with Streams
  • Concurrency versus Parallelism
  • Streams as Parallel Functional Pipelines
  • Parallel Streams in Action
  • When to Use and When to Avoid Parallel Streams
    • Choosing the Right Data Source
    • Number of Elements
    • Stream Operations
      • Pure lambdas
      • Parallel-friendly operations
      • Reduce versus collect
    • Stream Overhead and Available Resources
    • Example: War and Peace (revisited)
    • Example: Random Numbers
  • Parallel Streams Checklist
  • Takeaways
• 9. Handling null with Optionals
  • The Problem with null References
  • How to Handle null in Java (Before Optionals)
    • Best Practices for Handling null
      • Dont initialize a variable to null
      • Dont pass, accept, or return null
      • Check everything outside your control
      • null is acceptable as an implementation detail
      • When and when not to follow the rules
    • Tool-Assisted null Checks
    • Specialized Types Like Optional
  • Optionals to the Rescue
    • Whats an Optional?
    • Building Optional Pipelines
      • Creating an Optional
      • Checking for and reacting to values
      • Filtering and mapping
      • Getting a (fallback) value
  • Optionals and Streams
    • Optionals as Stream Elements
    • Terminal Stream Operations
      • Finding an element
      • Reducing to a single value
  • Optional Primitives
  • Caveats
    • Optionals Are Ordinary Types
    • Identity-Sensitive Methods
    • Performance Overhead
    • Special Considerations for Collections
    • Optionals and Serialization
  • Final Thoughts on null References
  • Takeaways
• 10. Functional Exception Handling
  • Java Exception Handling in a Nutshell
  • The try-catch block
    • The Different Types of Exceptions and Errors
      • Checked exceptions
      • Unchecked exceptions
      • Errors
      • Exception hierarchy in Java
  • Checked Exceptions in Lambdas
    • Safe Method Extraction
    • Un-Checking Exceptions
    • Sneaky Throws
  • A Functional Approach to Exceptions
    • Not Throwing Exceptions
    • Errors as Values
      • Creating the scaffold
      • Making Result<V, E> functional
    • The Try/Success/Failure Pattern
      • Creating a pipeline
      • Handling success and failure
      • Running the pipeline
  • Final Thoughts on Functional Exception Handling
  • Takeaways
• 11. Lazy Evaluation
  • Laziness Versus Strictness
  • How Strict Is Java?
    • Short-Circuit Evaluation
    • Control Structures
    • Lazy Types in the JDK
      • Lazy Maps
      • Streams
      • Optionals
  • Lambdas and Higher-Order Functions
    • An Eager Approach
    • A Lazier Approach
    • A Functional Approach
  • Delayed Executions with Thunks
    • Creating a Simple Thunk
    • A Thread-Safe Thunk
  • Final Thoughts on Laziness
  • Takeaways
• 12. Recursion
  • What Is Recursion?
    • Head Versus Tail Recursion
    • Recursion and the Call Stack
  • A More Complex Example
    • Iterative Tree Traversal
    • Recursive Tree Traversal
  • Recursion-Like Streams
  • Final Thoughts on Recursion
  • Takeaways
• 13. Asynchronous Tasks
  • Synchronous versus Asynchronous
  • Java Futures
  • Designing Asynchronous Pipelines with CompletableFutures
    • Promising a Value
    • Creating a CompletableFuture
    • Compositing and Combining Tasks
      • Compositing tasks
      • Combining tasks
      • Running more two CompletableFuture instances at once
    • Exception Handling
      • Data and error channel revisited
      • Rejected either tasks
    • Terminal Operations
    • Creating a CompletableFuture Helper
      • The helper scaffold
      • Designing eachOf
      • Improving the CompletableFutures helper
  • Manual Creation and Completion
    • Manual Creation
    • Manual Completion
    • Use Cases for Manually Created and Completed Instances
      • CompletableFutures as return values
      • Pending CompletableFuture pipelines
  • About Thread Pools and Timeouts
  • Final Thoughts on Asynchronous Tasks
  • Takeaways
• 14. Functional Design Patterns
  • What Are Design Patterns?
  • (Functional) Design Patterns
    • Factory Pattern
      • Object-oriented approach
      • A more functional approach
    • Decorator Pattern
      • Object-oriented approach
      • A more functional approach
    • Strategy Pattern
      • Object-oriented approach
      • A more functional approach
    • Builder Pattern
      • Object-oriented approach
      • A more functional approach
  • Final Thoughts on Functional Design Patterns
  • Takeaways
• 15. A Functional Approach to Java
  • OOP Versus FP Principles
  • A Functional Mindset
    • Functions Are First-Class Citizens
    • Avoiding Side Effects
      • Pure functions
      • Pure object methods
      • Isolating side effects
      • Favor expressions over statements
      • Moving toward immutability
    • Functional Data Processing with Map/Filter/Reduce
    • Abstractions Guide Implementations
    • Building Functional Bridges
      • Method references-friendly signatures
      • Using retroactive functional interfaces
      • Lambda factories for common operations
      • Implementing functional interfaces explicitly
      • Functional null handling with Optionals
    • Parallelism and Concurrency Made Easy
    • Be Mindful of Potential Overhead
  • Functional Architecture in an Imperative World
    • From Objects to Values
    • Separation of Concerns
    • The Different Sizes of an FC/IS
    • Testing an FC/IS
  • Final Thoughts on a Functional Approach to Java
  • Takeaways
• Index

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