Decorators in Software Design
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Decorators
Muddiest Point
Tomorrow:
Quiz on lab reading:
https://faculty-
web.msoe.edu/hasker/se2811/labs/5/
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Slide design: Dr. Mark L. Hornick
Content: Dr. Hornick
Errors: Dr. Yoder
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Any potential changes?
Keep current design?
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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
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Whip
Mocha
DarkRoast
cost()
cost()
cost()
0.99
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0.10
$1.29
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Wikipedia
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http://zishanbilal.files.wordpress.com/2011/04/042811_2030_designpatte31.png
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Reduce coupling
Increase cohesion
Encapsulate what varies
Favor composition over inheritance
Program to interfaces, not implementations
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Which of these are met?
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What are the disadvantages of decorators?
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<<deprecated>>
<<deprecated>>
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(with other
Variables…)
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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.
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Presentation Transcript
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
Coffee Inheritance Model Design Review Any potential changes? Keep current design? SE-2811 2 Dr. Mark L. Hornick
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
One approach: Inheritance SE-2811 4 Dr. Mark L. Hornick
Cleaned up with decorator pattern SE-2811 5 Dr. Mark L. Hornick
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
General Pattern SE-2811 7 Dr. Mark L. Hornick Wikipedia
Example 2: Byte Input Streams SE-2811 8 Dr. Mark L. Hornick
Ex 3: Bikes SE-2811 9 Dr. Mark L. Hornick
Ex 4: Employees SE-2811 10 Dr. Mark L. Hornick http://zishanbilal.files.wordpress.com/2011/04/042811_2030_designpatte31.png
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
Downsides What are the disadvantages of decorators? SE-2811 12 Dr. Mark L. Hornick
SE-2811 13 Dr. Mark L. Hornick
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
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
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
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
