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Grigoriu tudor 341 c5_(tudorgrigoriu@yahoo.com)_designpatterns

Tudor Grigoriu
Tudor Grigoriu

This document introduces software design patterns, which provide generalizable solutions to common design problems. It discusses three main categories of patterns: creational (Singleton, Factory), structural (Decorator), and behavioral (Command, Visitor, Observer). Examples are provided for the Singleton, Factory, and Decorator patterns. The Factory pattern shows how to dynamically create Dacia car objects based on their type. The Decorator pattern adds functionality like scrollbars to windows without changing the window class. Design patterns help rapidly and efficiently create system designs and understand existing systems.

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Design patterns (Sabloane de proiectare) Tudor Grigoriu 341C5
Introducere (I) Un design pattern este o solutie generala si reutilizabila a unei probleme comune in design-ul software Nu toate pattern-urile software sunt design patterns. De exemplu, algoritmii rezolva probleme computationale, nu probleme de design.
Introducere(II) De ce sa folosim Design Patterns? Pentru a crea rapid si eficient design-ul unui sistem software Pentru a intelege un sistem existent
Introducere (III)
Introducere (III) Categorii: Creational patterns Singleton Factory Structural Patterns Decorator Behavioral Patterns Command Visitor Observer
Creational Patterns
Singleton (I)
Singleton(II) public class BeerShop { private static final BeerShop INSTANCE = new Beershop(); // Constructorul private previne instantierea din cadrul altor clase private BeerShop() { //... } public static BeerShop getInstance() { return INSTANCE; } }
Factory Pattern
Factory Pattern (II) abstract class Dacia { public abstract double getPrice(); } class DaciaMD87 extends Dacia { public double getPrice() { return 8.5; } } class DaciaEstafette extends Dacia { public double getPrice() { return 10.5; } } class DaciaD33 extends Dacia { public double getPrice() { return 11.5; } }
Factory Pattern (III) class DaciaFactory { public enum DaciaType { DaciaMD87, DaciaEstafette, DaciaD33 } public static Dacia createDacia(DaciaType daciaType) { switch (daciaType) { case DaciaMD87: return new DaciaMD87(); case DaciaEstafette: return new DaciaEstafette(); case DaciaD33: return new DaciaD33(); } throw new IllegalArgumentException("The car type " + daciaType + " is not recognized."); } }
Factory Pattern (IV) class DaciaLover { public static void main (String args[]) { for (DaciaFactory.DaciaType daciaType : DaciaFactory.DaciaType.values()) { System.out.println("Price of " + daciaType + " is " + DaciaFactory.createDacia(daciaType).getPrice()); } } }
Structural Patterns
Decorator Permite adaugarea dinamica de noi comportamente unui obiect deja existent E o alternativa pentru folosirea de sub-clase.
Exemplu (I) Sa ne imaginam ca ...
Exemplu (II) interface Window { public void draw(); // deseneaza fereastra public String getDescription(); // o descriere a ferestrei } // fereastra simpla fara scrollbar class SimpleWindow implements Window { public void draw() { // draw window } public String getDescription() { return "simple window"; } }
Exemplu (III) abstract class WindowDecorator implements Window { protected Window decoratedWindow; // fereastra decorata public WindowDecorator (Window decoratedWindow) { this.decoratedWindow = decoratedWindow; } public void draw() { decoratedWindow.draw(); //delegation } public String getDescription() { return decoratedWindow.getDescription(); //delegation } }
Exemplu (IV) class VerticalScrollBarDecorator extends WindowDecorator { public VerticalScrollBarDecorator (Window decoratedWindow) { super(decoratedWindow); } @Override public void draw() { decoratedWindow.draw(); drawVerticalScrollBar(); } private void drawVerticalScrollBar() { // draw vertical scrollbar } @Override public String getDescription() { return decoratedWindow.getDescription() + ", including vertical scrollbars"; } }
Exemplu (V) class HorizontalScrollBarDecorator extends WindowDecorator { public HorizontalScrollBarDecorator (Window decoratedWindow) { super(decoratedWindow); } @Override public void draw() { decoratedWindow.draw(); drawHorizontalScrollBar(); } private void drawHorizontalScrollBar() { // draw the horizontal scrollbar } @Override public String getDescription() { return decoratedWindow.getDescription() + ", including horizontal scrollbars"; } }
Exemplu (VI) public class DecoratedWindowTest { public static void main(String[] args) { // creaza o fereastra decorata cu scrollbar orizontal/extern Window decoratedWindow = new HorizontalScrollBarDecorator ( new VerticalScrollBarDecorator(new SimpleWindow())); System.out.println(decoratedWindow.getDescription()); } }
Behavioral Patterns
Observer Pattern Cand un obiect isi schimba starea, toti dependentii lui sunt notificati si actualizati automat. Implicit exista un obiect subiect, care are o lista de obiecte dependente. Observatorii sunt obiectele ce sunt apelate automata de fiecare data cand subiectul face o actiune
Observer Pattern
Concluzii De ce sa folosim Design Patterns? Pentru a crea rapid si eficient design-ul unui sistem software Pentru a intelege un sistem existent Se cere la interviuri :) 3 categorii: Creational patterns: Singleton, Factory, Multiton Structural patterns: Decorator, Adaptor, Facade Behavioral patterns: Observer, Iterator, Strategy

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Grigoriu tudor 341 c5_(tudorgrigoriu@yahoo.com)_designpatterns

  • 1. Design patterns (Sabloane de proiectare) Tudor Grigoriu 341C5
  • 2. Introducere (I) Un design pattern este o solutie generala si reutilizabila a unei probleme comune in design-ul software Nu toate pattern-urile software sunt design patterns. De exemplu, algoritmii rezolva probleme computationale, nu probleme de design.
  • 3. Introducere(II) De ce sa folosim Design Patterns? Pentru a crea rapid si eficient design-ul unui sistem software Pentru a intelege un sistem existent
  • 5. Introducere (III) Categorii: Creational patterns Singleton Factory Structural Patterns Decorator Behavioral Patterns Command Visitor Observer
  • 8. Singleton(II) public class BeerShop { private static final BeerShop INSTANCE = new Beershop(); // Constructorul private previne instantierea din cadrul altor clase private BeerShop() { //... } public static BeerShop getInstance() { return INSTANCE; } }
  • 10. Factory Pattern (II) abstract class Dacia { public abstract double getPrice(); } class DaciaMD87 extends Dacia { public double getPrice() { return 8.5; } } class DaciaEstafette extends Dacia { public double getPrice() { return 10.5; } } class DaciaD33 extends Dacia { public double getPrice() { return 11.5; } }
  • 11. Factory Pattern (III) class DaciaFactory { public enum DaciaType { DaciaMD87, DaciaEstafette, DaciaD33 } public static Dacia createDacia(DaciaType daciaType) { switch (daciaType) { case DaciaMD87: return new DaciaMD87(); case DaciaEstafette: return new DaciaEstafette(); case DaciaD33: return new DaciaD33(); } throw new IllegalArgumentException("The car type " + daciaType + " is not recognized."); } }
  • 12. Factory Pattern (IV) class DaciaLover { public static void main (String args[]) { for (DaciaFactory.DaciaType daciaType : DaciaFactory.DaciaType.values()) { System.out.println("Price of " + daciaType + " is " + DaciaFactory.createDacia(daciaType).getPrice()); } } }
  • 14. Decorator Permite adaugarea dinamica de noi comportamente unui obiect deja existent E o alternativa pentru folosirea de sub-clase.
  • 15. Exemplu (I) Sa ne imaginam ca ...
  • 16. Exemplu (II) interface Window { public void draw(); // deseneaza fereastra public String getDescription(); // o descriere a ferestrei } // fereastra simpla fara scrollbar class SimpleWindow implements Window { public void draw() { // draw window } public String getDescription() { return "simple window"; } }
  • 17. Exemplu (III) abstract class WindowDecorator implements Window { protected Window decoratedWindow; // fereastra decorata public WindowDecorator (Window decoratedWindow) { this.decoratedWindow = decoratedWindow; } public void draw() { decoratedWindow.draw(); //delegation } public String getDescription() { return decoratedWindow.getDescription(); //delegation } }
  • 18. Exemplu (IV) class VerticalScrollBarDecorator extends WindowDecorator { public VerticalScrollBarDecorator (Window decoratedWindow) { super(decoratedWindow); } @Override public void draw() { decoratedWindow.draw(); drawVerticalScrollBar(); } private void drawVerticalScrollBar() { // draw vertical scrollbar } @Override public String getDescription() { return decoratedWindow.getDescription() + ", including vertical scrollbars"; } }
  • 19. Exemplu (V) class HorizontalScrollBarDecorator extends WindowDecorator { public HorizontalScrollBarDecorator (Window decoratedWindow) { super(decoratedWindow); } @Override public void draw() { decoratedWindow.draw(); drawHorizontalScrollBar(); } private void drawHorizontalScrollBar() { // draw the horizontal scrollbar } @Override public String getDescription() { return decoratedWindow.getDescription() + ", including horizontal scrollbars"; } }
  • 20. Exemplu (VI) public class DecoratedWindowTest { public static void main(String[] args) { // creaza o fereastra decorata cu scrollbar orizontal/extern Window decoratedWindow = new HorizontalScrollBarDecorator ( new VerticalScrollBarDecorator(new SimpleWindow())); System.out.println(decoratedWindow.getDescription()); } }
  • 22. Observer Pattern Cand un obiect isi schimba starea, toti dependentii lui sunt notificati si actualizati automat. Implicit exista un obiect subiect, care are o lista de obiecte dependente. Observatorii sunt obiectele ce sunt apelate automata de fiecare data cand subiectul face o actiune
  • 24. Concluzii De ce sa folosim Design Patterns? Pentru a crea rapid si eficient design-ul unui sistem software Pentru a intelege un sistem existent Se cere la interviuri :) 3 categorii: Creational patterns: Singleton, Factory, Multiton Structural patterns: Decorator, Adaptor, Facade Behavioral patterns: Observer, Iterator, Strategy