Functional Programming in Java, Second Edition

Imagine writing Java code that reads like the problem statement, code that's highly expressive, concise, easy to read and modify, and has reduced complexity. With the functional programming capabilities in Java, that's not a fantasy. This book will guide you from the familiar imperative style through the practical aspects of functional programming, using plenty of examples. Apply the techniques you learn to turn highly complex imperative code into elegant and easy-to-understand functional-style code. Updated to the latest version of Java, this edition has four new chapters on error handling, refactoring to functional style, transforming data, and idioms of functional programming. Don't struggle with the limitations of the imperative style; instead learn to combine object-oriented programming with the functional style to reduce the accidental complexity. Harness the functional programming capabilities of Java to create applications where the program reveals its intentions and your team can quickly understand and modify code to align with changing business requirements. Unlock the power of lambda expressions and the Streams API to turn the oft-written spaghetti code into highly concise, expressive, elegant, and maintainable code. See how Streams make the arduous task of parallelizing code as easy as flipping a switch when superior speed is necessary. Apply design patterns built around lambda expressions, safely manage resource allocations, use memoization, and learn to transform data into different forms, all while honoring immutability, and providing thread safety to leverage lazy evaluation for efficiency and parallel execution for performance. Move beyond the basics, explore the idioms for writing functional programs. Learn to think functionally by refactoring legacy code into the functional style. And, if your code runs aground due to failures, learn to properly handle errors the functional way. Don't drown in theory; instead learn the practical functional programming techniques to create superior Java code. What You Need Java version 8 or newer. Functional Programming in Java, S econd Edition About the Pragmatic Bookshelf Table of Contents Foreword to the First Edition Praise for Functional Programming in Java, Second Editio n Acknowledgments Preface Who’s This Book For What’s in This Book Java Version Used in This Book How to Read the Code Examples Online Resources Chapter 1: Hello, Lambda Expressions! Change the Way You Think The Big Gains of Functional-Style Code Why Code in the Functional Style? Evolution, Not Revolution A Little Sugar to Sweeten Wrapping Up Chapter 2: Using Collections Iterating through a List Transforming a List Finding Elements Skipping Values Terminating Iterations Reusing Lambda Expressions Using Lexical Scoping and Closures Picking an Element Reducing a Collection to a Single Value Joining Elements Wrapping Up Chapter 3: Strings, Comparators, and Filters Iterating a String Implementing the Comparator Interface Multiple and Fluent Comparisons Using the collect Method and the Collectors Class Listing All Files in a Directory Listing Select Files in a Directory Listing Immediate Subdirectories Using flatMap Watching a File Change Wrapping Up Chapter 4: Transforming Data Computing Statistics When to Use map vs. flatMap Checking for Criteria Partitioning a Collection Counting Occurrences Summing Values Using flatMapping and filtering Teeing Operations Wrapping Up Chapter 5: Designing with Lambda Expressions Separating Concerns Using Lambda Express ions Delegating Using Lambda Expressions Decorating Using Lambda Expressions A Peek into the default Methods Creating Fluent Interfaces Using L ambda Expressions Wrapping Up Chapter 6: Working with Resources Cleaning Up Resources Using the Execute Around Method Pattern to Cl ean Up Resources Managing Locks Creating Concise Exception Tests Wrapping Up Chapter 7: Being Lazy Delayed Initialization Lazy Evaluations Leveraging the Laziness of Str eams Creating Infinite, Lazy Collec tions Wrapping Up Chapter 8: Optimizing Recursions Using Tail-Call Optimization Speeding Up with Memoization Wrapping Up Chapter 9: Composing Functions with Lambda Expressions Using Function Composition Using MapReduce Taking a Leap to Parallelize Wrapping Up Chapter 10: Error Handling Taking a Holistic View of Error Handling Exception Handling and Imperative Style Checked Exceptions and Functional Style with Streams Exception Handling vs. Functional Style Dealing with It Downstream Handling Failures in Functional Programming Wrapping Up Chapter 11: Refactoring to Functional Style Creating a Safety Net for Refactoring Refactoring the Traditional for Loop Refactoring More Complex Loops Refactoring Unbounded Loops Refactoring for-each Refactoring to Rework the Logic Refactoring File Processing Refactoring Data Grouping Operations Refactoring Nested Loops Real-World Refactoring Wrapping Up Chapter 12: Functional Programming Idioms Don’t Write Dense Lambda Expressions Prefer Method References Properly Structure the Functional Pipeline Keep Separate Conditions in Separate Filters Provide Good Domain-Specific Parameter Names Use Type Inference for Parameters Side Effects in Functional Pipelines Wrapping Up Chapter 13: Bringing It All Together Essential Practices to Succeed with the Functional Style Performance Concerns Adopting the Functional Style Appendix 1: Starter Set of Functional Interfaces Consumer Supplier Predicate Function Appendix 2: Syntax Overview Defining a Functional Interface Creating No-Parameter Lambda Expressions Creating a Single-Parameter Lambda Expression Inferring a Lambda Expression’s Parameter Typ e Dropping Parentheses for a Single-Parameter I nferred Type Creating a Multi-Parameter Lambda Expression Calling a Method with Mixed Parameters Storing a Lambda Expression Creating a Multiline Lambda Expression Returning a Lambda Expression Returning a Lambda Expression from a Lambda E xpression Lexical Scoping in Closures Passing a Method Reference of an Instance Met hod Passing a Method Reference to a static Method Passing a Method Reference to a Method on Ano ther Instance Passing a Reference of a Method That Takes Pa rameters Using a Constructor Reference Function Composition Appendix 3: Web Resources Bibliography You May Be Interested In...