Java OOP Done Right
Java OOP Done Right
The down-to-earth guide to clean, clear, elegant object oriented code in modern Java
About the Book
Object Oriented Programming in Java - Done Right!
You've seen awful Java code and you're sick of it. Wasn't OOP supposed to make programming easier? Why is this code so bad?
Because it was done wrong, that's why. It wasn't even OOP code. It was a tangled mess of getters and setters, giant untestable methods and organised so badly, you'd think the keyboard just fell down some stairs.
We're going to learn how to do it right. You will learn:
- Designing objects with behaviours and secrets
- What encapsulation really means
- Simplifying conditional code with polymorphism
- Using Test Driven Development to find behaviours
- SOLID principles - understand them, use them
- Design Patterns you will actually use
- Refactoring - improving your code as you learn more
- Hexagonal Architecture - decoupling external systems to improve test
- Handling errors with style
- OOP Mistakes - how to avoid them
With your next project, you're going to code Java OOP like a champ.
Craft code you can be proud of!
About the Author
Table of Contents
- Preface
- Optimise for Clarity
-
What is an object, anyway?
- What’s all this got to do with Java?
- A simple example: Greeting users
- The big idea: calling code is simple
- Object Oriented Design is Behaviour Driven Design
-
Clean Code
- Good Names
- Design methods around behaviours, not data
- Hidden data - No getters, no setters
-
Aggregates: More than one
- Greeting more than one user
- Using forEach - not a loop
- Aggregate methods work on all the things
-
Collaboration
- Basic Mechanics
- Example: Simple Point of Sale
-
Test Driven Development
- Outside-in design with TDD
- First test: total starts at zero
- Arrange, Act, Assert - a rhythm inside each test
- Red, Green, Refactor - a rhythm in between tests
- Second test: Adding an item gives us the right total
- Designing the second feature
- TDD Steps - Too much? Too little?
- YAGNI - You Ain’t Gonna Need It
- YAYA - Yes, You Are
- Optimise for Clarity with well-named tests
- TDD and OOP - A natural fit
- FIRST Tests are usable tests
- Real-world TDD
-
Polymorphism - The Jewel in the OOP Crown
- Classic example: Shape.draw()
- The Shape Interface
- Tell Don’t Ask - the key to OOP
-
The SOLID Principles
- The five SOLID principles
- SRP Single Responsibility - do one thing well
- DIP Dependency Inversion: Bring out the Big Picture
- LSP Liskov Substitution Principle - Making things swappable
- OCP Open/Closed Principle - adding without change
- ISP Interface Segregation Principle - honest interfaces
-
TDD and Test Doubles
- Test Doubles - Stubs and Mocks
- DIP for Unit Tests - Stubs and Mocks
- Mocking libraries
- Self-Shunt mocks and stubs
-
Refactoring
- What is refactoring?
- Rename Method, Rename Variable
- Extract Method
- Change Method Signature
- Extract Parameter Object
- Can we refactor anything into anything else?
-
Hexagonal Architecture
- The problems of external systems
- The Test Pyramid
- Removing external systems
- The Hexagonal Model
- Inversion / Injection: Two sides of the same coin
-
Handling Errors
- Three kinds of errors
- The null reference
- Null object pattern
- Zombie object
- Exceptions - a quick primer
- Design By Contract, Bertrand Meyer style
- Fatal errors: Stop the world!
- Combined approach: Fixable and non-fixable errors
- Which approach is best?
- NullPointerException
- Application Specific Exceptions
- Error object
- Optionals - Java 8 streams approach
- Review: Which approach to use?
-
Design Patterns
- Mechanism and Domain
- Patterns: Not libraries, not frameworks
- Strategy
- Observer
- Adapter
- Command
- Composite
- Facade
- Builder
- Repository
- Query
- CollectingParameter
- Item-Item Description
- Moment-Interval
- Clock
- Rules (or Policy)
- Aggregate
- Cache
- Decorator
- External System (Proxy)
- Configuration
- Order-OrderLineItem
- Request-Service-Response
- Anti-Patterns
-
OOP Mistakes - OOP oops!
- Broken Encapsulation - Getters Galore!
- Broken Inheritance
- Bird extends Animal
- Square extends Rectangle
- Inheriting implementation
- Broken Shared State
- Ordinary Bad Code
-
Data Structures and Pure Functions
- System Boundaries
- Fixed Data, Changing Functions
- Algorithms and Data Structures
-
Putting It All Together
- No step-by-step plans
- Getting Started
- Perfection and Pragmatism
- Getting Past Stuck
-
Further Reading
- Agile Software Development, Robert C Martin
- Growing Object Oriented Software Guided By Tests, Freeman and Pryce
- Refactoring, Martin Fowler
- Design Patterns Helm, Johnson, Richards, Vlissides
- Domain Driven Design, Eric Evans
- Applying UML with Patterns, Craig Larman
- Home page for this book
- My Blog
- My Quora Space
- LeanPub page
-
Cheat Sheet
- Behaviours First
- Design Principles
- Clean Code
- General Code Review Points
-
About the Author
- Thanks
- Notes
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