Head First Design Patterns: Building Extensible and Maintainable Object-Oriented Software, 2nd Edition

go to link Creators of the Head First Series Table of Contents (the real thing) Intro: How to use this Book Who is this book for? Who should probably back away from this book? We know what you’re thinking. And we know what your brain is thinking. Metacognition: thinking about thinking Here’s what WE did: Here’s what YOU can do to bend your brain into submission Read Me We use simple UML-like diagrams. We don’t cover every single Design Pattern ever created. The activities are NOT optional. We use the word “composition” in the general OO sense, which is more flexible than the strict UML use of “composition.” The redundancy is intentional and important. The code examples are as lean as possible. The Brain Power exercises don’t have answers. Tech Reviewers Tech Reviewers, 2nd Edition Acknowledgments From the first edition Acknowledgments From the second edition Very Special Thanks 1. Welcome to Design Patterns: Intro to Design Patterns It started with a simple SimUDuck app But now we need the ducks to FLY But something went horribly wrong... Joe thinks about inheritance... How about an interface? What would you do if you were Joe? The one constant in software development Zeroing in on the problem... Separating what changes from what stays the same Designing the Duck Behaviors Implementing the Duck Behaviors there are no Dumb Questions Integrating the Duck Behaviors More integration... Testing the Duck code Setting behavior dynamically The Big Picture on encapsulated behaviors HAS-A can be better than IS-A Speaking of Design Patterns... Design Puzzle Overheard at the local diner... Overheard in the next cubicle... The power of a shared pattern vocabulary How do I use Design Patterns? there are no Dumb Questions Tools for your Design Toolbox Design Patterns Crossword Design Puzzle Solution Design Patterns Crossword Solution 2. Keeping your Objects in the Know: The Observer Pattern The Weather Monitoring application overview Unpacking the WeatherData class Our Goal Stretch Goal Taking a first, misguided implementation of the Weather Station What’s wrong with our implementation anyway? Meet the Observer Pattern Publishers + Subscribers = Observer Pattern A day in the life of the Observer Pattern Five-minute drama: a subject for observation Two weeks later... The Observer Pattern defined The Observer Pattern: the Class Diagram there are no Dumb Questions The Power of Loose Coupling Cubicle conversation Designing the Weather Station Implementing the Weather Station Implementing the Subject interface in WeatherData Now, let’s build those display elements there are no Dumb Questions Power up the Weather Station Looking for the Observer Pattern in the Wild The Swing library A little life-changing application Coding the life-changing application there are no Dumb Questions Meanwhile, back at Weather-O-Rama For the Subject to send notifications... For an Observer to receive notifications... Code Magnets Test Drive the new code Tools for your Design Toolbox Design Principle Challenge Design Patterns Crossword Design Principle Challenge Solution Code Magnets Solution Design Patterns Crossword Solution 3. Decorating Objects: The Decorator Pattern Welcome to Starbuzz Coffee The Open-Closed Principle there are no Dumb Questions Meet the Decorator Pattern Constructing a drink order with Decorators Okay, here’s what we know about Decorators, so far... The Decorator Pattern defined Decorating our Beverages Cubicle Conversation New barista training Writing the Starbuzz code Coding beverages Coding condiments Serving some coffees there are no Dumb Questions Real-World Decorators: Java I/O Decorating the java.io classes Writing your own Java I/O Decorator Test out your new Java I/O Decorator Tools for your Design Toolbox 4. Baking with OO Goodness: The Factory Pattern Identifying the aspects that vary But the pressure is on to add more pizza types Encapsulating object creation Building a simple pizza factory there are no Dumb Questions Reworking the PizzaStore class The Simple Factory defined Franchising the pizza store We’ve seen one approach... But you’d like a little more quality control... A framework for the pizza store Allowing the subclasses to decide Let’s make a Pizza Store Declaring a factory method Let’s see how it works: ordering pizzas with the pizza factory method So how do they order? Let’s check out how these pizzas are really made to order... We’re just missing one thing: Pizzas! Our Pizza Store isn’t going to be very popular without some pizzas, so let’s implement them Now we just need some concrete subclasses...how about defining New York and Chicago-style cheese pizzas? You’ve waited long enough. Time for some pizzas! It’s finally time to meet the Factory Method Pattern The Creator classes The Product classes View Creators and Products in Parallel Design Puzzle Factory Method Pattern defined there are no Dumb Questions Looking at object dependencies The Dependency Inversion Principle Applying the Principle Inverting your thinking... A few guidelines to help you follow the Principle... Meanwhile, back at the Pizza Store... Ensuring consistency in your ingredients Families of ingredients... Building the ingredient factories Building the New York ingredient factory Reworking the pizzas... Reworking the pizzas, continued... Revisiting our pizza stores What have we done? More pizza for Ethan and Joel... Ethan and Joel can’t get enough Objectville Pizza! What they don’t know is that now their orders are making use of the new ingredient factories. So now when they order... From here things change, because we are using an ingredient factory Abstract Factory Pattern defined Factory Method and Abstract Factory compared Tools for your Design Toolbox Design Patterns Crossword Design Puzzle Solution Design Patterns Crossword Solution 5. One-of-a-Kind Objects: The Singleton Pattern The Little Singleton A small Socratic exercise in the style of The Little Lisper Dissecting the classic Singleton Pattern implementation The Chocolate Factory Singleton Pattern defined Hershey, PA, we have a problem... BE the JVM Dealing with multithreading Can we improve multithreading? 1. Do nothing if the performance of getInstance() isn’t critical to your application. 2. Move to an eagerly created instance rather than a lazily created one. 3. Use “double-checked locking” to reduce the use of synchronization in getInstance(). Meanwhile, back at the Chocolate Factory... Congratulations! there are no Dumb Questions Tools for your Design Toolbox Design Patterns Crossword Design Patterns Crossword Solution 6. Encapsulating Invocation: The Command Pattern Home Automation or Bust, Inc. Free hardware! Let’s check out the Remote Control... Taking a look at the vendor classes Cubicle Conversation Meanwhile, back at the Diner..., or, A brief introduction to the Command Pattern Let’s study the interaction in a little more detail... The Objectville Diner roles and responsibilities From the Diner to the Command Pattern Our first command object Using the command object Creating a simple test to use the Remote Control The Command Pattern defined The Command Pattern defined: the class diagram Assigning Commands to slots Implementing the Remote Control Implementing the Commands Putting the Remote Control through its paces Now, let’s check out the execution of our remote control test... Time to write that documentation... What are we doing? Time to QA that Undo button! Using state to implement Undo Adding Undo to the Ceiling Fan commands Get ready to test the ceiling fan Testing the ceiling fan... Every remote needs a Party Mode! Using a macro command there are no Dumb Questions More uses of the Command Pattern: queuing requests More uses of the Command Pattern: logging requests Command Pattern in the Real World Tools for your Design Toolbox Design Patterns Crossword 7. Being Adaptive: The Adapter and Facade Patterns Adapters all around us Object-oriented adapters If it walks like a duck and quacks like a duck, then it must might be a duck turkey wrapped with a duck adapter... Test drive the adapter The Adapter Pattern explained Here’s how the Client uses the Adapter there are no Dumb Questions Adapter Pattern defined Object and class adapters Duck Magnets Duck Magnets Answer Real-world adapters Enumerators Iterators Using Enumerators with code that expects Iterators Adapting an Enumeration to an Iterator Designing the Adapter Dealing with the remove() method Writing the EnumerationIterator adapter And now for something different... Home Sweet Home Theater Watching a movie (the hard way) Lights, Camera, Facade! there are no Dumb Questions Constructing your home theater facade Implementing the simplified interface Time to watch a movie (the easy way) Facade Pattern defined The Principle of Least Knowledge How NOT to Win Friends and Influence Objects Keeping your method calls in bounds... there are no Dumb Questions The Facade Pattern and the Principle of Least Knowledge Tools for your Design Toolbox Design Patterns Crossword Design Patterns Crossword Solution 8. Encapsulating Algorithms: The Template Method Pattern It’s time for some more caffeine Whipping up some coffee and tea classes (in Java) And now the Tea... Let’s abstract that Coffee and Tea Taking the design further... Abstracting prepareRecipe() What have we done? Meet the Template Method Let’s make some tea... What did the Template Method get us? Template Method Pattern defined Hooked on Template Method... Using the hook Let’s run the Test Drive And let’s give it a run... there are no Dumb Questions The Hollywood Principle The Hollywood Principle and Template Method there are no Dumb Questions Template Methods in the Wild Sorting with Template Method We’ve got some ducks to sort... What is compareTo()? Comparing Ducks and Ducks Let’s sort some Ducks Let the sorting commence! The making of the sorting duck machine there are no Dumb Questions Swingin’ with Frames Custom Lists with AbstractList Design Patterns Crossword Tools for your Design Toolbox Design Patterns Crossword Solution 9. Well-Managed Collections: The Iterator and Composite Patterns Breaking News: Objectville Diner and Objectville Pancake House Merge Check out the Menu Items Lou and Mel’s Menu implementations What’s the problem with having two different menu representations? The Java-Enabled Waitress Specification Implementing the spec: our first attempt What now? Can we encapsulate the iteration? Meet the Iterator Pattern Adding an Iterator to DinerMenu Reworking the DinerMenu with Iterator Fixing up the Waitress code Testing our code Here’s the test run... What have we done so far? Reviewing our current design... Making some improvements... there are no Dumb Questions Cleaning things up with java.util.Iterator We are almost there... What does this get us? Iterator Pattern defined The Iterator Pattern Structure The Single Responsibility Principle there are no Dumb Questions Meet Java’s Iterable interface Java’s enhanced for loop Not so fast; Arrays are not Iterables Taking a look at the Café Menu Reworking the Café Menu code Adding the Cafe Menu to the Waitress Breakfast, lunch, AND dinner Here’s the test run; check out the new dinner menu from the Café! What did we do? We decoupled the Waitress.... ...and we made the Waitress more extensible But there’s more! Iterators and Collections Code Magnets Is the Waitress ready for prime time? Just when we thought it was safe... What do we need? The Composite Pattern defined there are no Dumb Questions Designing Menus with Composite Implementing MenuComponent Implementing the MenuItem Implementing the Composite Menu Fixing the print() method Getting ready for a test drive... Now for the test drive... Getting ready for a test drive... Design Patterns Crossword Tools for your Design Toolbox Code Magnets Solution Design Patterns Crossword Solution 10. The State of Things: The State Pattern Java Breakers Cubicle Conversation State machines 101 Writing the code In-house testing You knew it was coming...a change request! Design Puzzle The messy STATE of things... The new design Defining the State interfaces and classes Implementing our State classes Reworking the Gumball Machine Now, let’s look at the complete GumballMachine class... Implementing more states Let’s take a look at what we’ve done so far... The State Pattern defined there are no Dumb Questions We still need to finish the Gumball 1 in 10 game Finishing the game Demo for the CEO of Mighty Gumball, Inc. there are no Dumb Questions Sanity check... We almost forgot! Tools for your Design Toolbox Design Puzzle Solution 11. Controlling Object Access: The Proxy Pattern Coding the Monitor Testing the Monitor The role of the ‘remote proxy’ Adding a remote proxy to the Gumball Machine monitoring code Remote methods 101 Walking through the design How the method call happens Java RMI, the Big Picture Making the Remote service Step one: make a Remote interface Step two: make a Remote implementation Step four: start the service Step four: start the service there are no Dumb Questions Complete code for the server side Complete code for the client side Back to our GumballMachine remote proxy Getting the GumballMachine ready to be a remote service Registering with the RMI registry... Now for the GumballMonitor client... Writing the Monitor test drive Another demo for the CEO of Mighty Gumball... And now let’s put the monitor in the hands of the CEO. Hopefully, this time he’ll love it: The Proxy Pattern defined Get ready for the Virtual Proxy Remote Proxy Virtual Proxy Displaying Album covers Designing the Album Cover Virtual Proxy How ImageProxy is going to work: Writing the Image Proxy Testing the Album Cover Viewer Things to try... What did we do? there are no Dumb Questions Using the Java API’s Proxy to create a protection proxy Geeky Matchmaking in Objectville The Person implementation Five-minute drama: protecting subjects Big Picture: creating a Dynamic Proxy for the Person Step one: creating Invocation Handlers Creating Invocation Handlers, continued... Step two: creating the Proxy class and instantiating the Proxy object Testing the matchmaking service Running the code... there are no Dumb Questions The Proxy Zoo Design Patterns Crossword Tools for your Design Toolbox Design Patterns Crossword Solution The code for the Album Cover Viewer 12. Patterns of Patterns: Compound Patterns Working together Duck reunion there are no Dumb Questions What did we do? A duck’s-eye view: the class diagram The King of Compound Patterns If Elvis were a compound pattern, his name would be Model-View-Controller, and he’d be singing a little song like this... Meet Model-View-Controller A closer look... there are no Dumb Questions Understanding MVC as a set of Patterns Observer Strategy Composite Using MVC to control the beat... Meet the Java DJ View The controller is in the middle... Let’s not forget about the model underneath it all... Putting the pieces together Building the pieces Let’s check out the BeatModelInterface before looking at the implementation: Now let’s have a look at the concrete BeatModel class The View Implementing the View Now for the Controller And here’s the implementation of the controller: Putting it all together... And now for a test run... Things to try Exploring Strategy Adapting the Model Now we’re ready for a HeartController And that’s it! Now it’s time for some test code... And now for a test run... Things to try there are no Dumb Questions Tools for your Design Toolbox Exercise Solutions The Beat Model The View The Controller The Heart Model The Heart Adapter The Controller 13. Patterns in the Real World: Better Living with Patterns Design Pattern defined Looking more closely at the Design Pattern definition there are no Dumb Questions So you wanna be a Design Patterns writer Organizing Design Patterns Pattern Categories Thinking in Patterns Keep it simple (KISS) Design Patterns aren’t a magic bullet; in fact, they’re not even a bullet! You know you need a pattern when... Refactoring time is Patterns time! Take out what you don’t really need. Don’t be afraid to remove a Design Pattern from your design. If you don’t need it now, don’t do it now. Your Mind on Patterns Don’t forget the power of the shared vocabulary Cruisin’ Objectville with the Gang of Four Your journey has just begun... The definitive Design Patterns text The definitive Patterns texts Other Design Patterns resources The Patterns Zoo Annihilating evil with Anti-Patterns Tools for your Design Toolbox Leaving Objectville... Boy, it’s been great having you in Objectville. A. Leftover Patterns Bridge Your dilemma Why use the Bridge Pattern? Builder You need a flexible design Why use the Builder Pattern? Chain of Responsibility A scenario Your task How to use the Chain of Responsibility Pattern Flyweight A scenario Your big client’s dilemma Why use the Flyweight Pattern? Interpreter A scenario Now what? How to implement an interpreter Mediator A scenario HouseOfTheFuture’s dilemma Mediator in action... Memento A scenario The Memento at work Prototype A scenario Prototype to the rescue Visitor A scenario The Visitor drops by Index