Understanding Decorators in Software Design

Dive into the world of decorators in software design with Dr. Mark L. Hornick. Explore topics such as decorator patterns, inheritance, design principles, and more. Get ready for a quiz on lab readings and discover how to enhance your coffee model with decorators. Learn about reducing coupling, increasing cohesion, and encapsulating variations in your designs.

• Decorators
• Software Design
• Dr. Mark L. Hornick
• Design Principles
• Inheritance

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1. Week 5, Day 2: Decorator Decorators Muddiest Point Tomorrow: Quiz on lab reading: https://faculty- web.msoe.edu/hasker/se2811/labs/5/ SE-2811 1 Slide design: Dr. Mark L. Hornick Content: Dr. Hornick Errors: Dr. Yoder

2. Coffee Inheritance Model Design Review Any potential changes? Keep current design? SE-2811 2 Dr. Mark L. Hornick

3. Time for Coffee 2.0 Want to be able to add, Whip, Mocha, DarkRoast, etc. to our coffee Exercise: With your team, create a design to include these decorators and have the cost function return their cost SE-2811 3 Dr. Mark L. Hornick

4. One approach: Inheritance SE-2811 4 Dr. Mark L. Hornick

5. Cleaned up with decorator pattern SE-2811 5 Dr. Mark L. Hornick

6. Cost of DarkRoast with Whip and Mocha cost() cost() cost() 0.10 0.20 0.99 $1.29 DarkRoast Mocha Whip SE-2811 6 Dr. Mark L. Hornick

7. General Pattern SE-2811 7 Dr. Mark L. Hornick Wikipedia

8. Example 2: Byte Input Streams SE-2811 8 Dr. Mark L. Hornick

9. Ex 3: Bikes SE-2811 9 Dr. Mark L. Hornick

10. Ex 4: Employees SE-2811 10 Dr. Mark L. Hornick http://zishanbilal.files.wordpress.com/2011/04/042811_2030_designpatte31.png

11. Design Principles Reduce coupling Increase cohesion Encapsulate what varies Favor composition over inheritance Program to interfaces, not implementations Classes should be open for extension but closed for modification Which of these are met? SE-2811 11 Dr. Mark L. Hornick

12. Downsides What are the disadvantages of decorators? SE-2811 12 Dr. Mark L. Hornick

13. SE-2811 13 Dr. Mark L. Hornick

14. Knowing that the input stream classes are based on the Decorator pattern can make things easier class Input Stream Decorators io::FilterInputStream io::InputStream # in: volatile InputStream - - SKIP_BUFFER_SIZE: int = 2048 {readOnly} skipBuffer: byte ([]) # FilterInputStream(InputStream) + read() : int + read(byte[]) : int + read(byte[], int, int) : int + skip(long) : long + available() : int + close() : void + mark(int) : void + reset() : void + markSupported() : boolean + read() : int + read(byte[]) : int + read(byte[], int, int) : int + skip(long) : long + available() : int + close() : void + mark(int) : void + reset() : void + markSupported() : boolean #in io:: BufferedInputStream io::PipedInputStream io:: LineNumberInputStream io::FileInputStream <<deprecated>> io::StringBufferInputStream <<deprecated>> SE-2811 14 Dr. Mark L. Hornick

15. The Decorator pattern applied to output streams class Output Stream Decorators io::FilterOutputStream io::OutputStream # out: OutputStream + write(int) : void + write(byte[]) : void + write(byte[], int, int) : void + flush() : void + close() : void + FilterOutputStream(OutputStream) + write(int) : void + write(byte[]) : void + write(byte[], int, int) : void + flush() : void + close() : void #out io:: io:: io::DataOutputStream ObjectOutputStream PipedOutputStream io::FileOutputStream Writer io::PrintWriter Appendable io::PrintStream -psOut (with other Variables ) SE-2811 15 Dr. Mark L. Hornick

16. Threading Muddiest Point [To be revisited in a future lecture] Lambda examples Lambda examples Lambda vs. Anon inner syntax Java 8 Quiz Lambda examples Lambda examples "Effectively Final" All lambda examples the same code? Lambda examples When would you use a Lambda expression over an anonymous class and vice versa? The Lambda is a Java thing, not an intelliJ thing right? whens the next quiz? Agree More examples of using lambdas (didn't get exposure in software dev 2) Effectively Final? SE-2811 16 Dr. Mark L. Hornick

17. Patterns Muddiest Point [To be revisited in a future leture] We really didn't cover any sorting algorithms and what each's benefits are Can we do an example??? Related to the quiz for below question Do we need to implement code versions of the strategy and factory method patterns?? If so how extensive and will it be similar to how we implemented in class? Implementing the methods needed for the factory method pattern. Is there a flowchart/checklist to determine which pattern is more appropriate to use? Choosing the correct design pattern What are Coupling and Cohesion and is it better to have high or low coupling or cohesion? On a quiz/test would you ask us to draw the uml of a particular general pattern, or would you just ask us to write the code? Why would we use Factory Pattern? How do you know when to use what pattern to solve a problem? Diagrams High/Low Cohesion/Coupling Class Diagram for Factory Design Pattern Nothing 17