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DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used.COMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from the FACTORY METHOD PATTERNFACTORY PATTERN
ABSTRACT FACTORY PATTERN Abstract Factory offers the interface for creating a family of related objects, without explicitly specifying their classes.Abstract Factory is a super-factory which creates other factories (Factory offactories).
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used.COMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to defineADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance).COMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through a OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.PROXY PATTERN
The Proxy design pattern is applicable when there is a need to control access to an Object, as well as when there is a need for a sophisticated reference to an Object. Common Situations where the proxy pattern is applicable are: Virtual Proxies: delaying the creation and initialization of expensive objects until needed, wherethe objects are
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofSINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object.FLYWEIGHT PATTERN
Flyweight Pattern Motivation. Some programs require a large number of objects that have some shared state among them. Consider for example a game of war, were there is a large number of soldier objects; a soldier object maintain the graphical representation of a soldier, soldier behavior such as motion, and firing weapons, in addition soldier’s health and location on the war terrain. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand. DEPENDENCY INVERSION PRINCIPLE Below is the code which supports the Dependency Inversion Principle. In this new design a new abstraction layer is added through the IWorker Interface. Now the problems from the above code are solved (considering there is no change in the high level logic): Manager class doesn't require changes when adding SuperWorkers.DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to defineCOMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through aADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance). OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.SINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object.PROXY PATTERN
The Proxy design pattern is applicable when there is a need to control access to an Object, as well as when there is a need for a sophisticated reference to an Object. Common Situations where the proxy pattern is applicable are: Virtual Proxies: delaying the creation and initialization of expensive objects until needed, wherethe objects are
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend of ABSTRACT FACTORY PATTERN Abstract Factory offers the interface for creating a family of related objects, without explicitly specifying their classes.Abstract Factory is a super-factory which creates other factories (Factory offactories).
FLYWEIGHT PATTERN
Flyweight Pattern Motivation. Some programs require a large number of objects that have some shared state among them. Consider for example a game of war, were there is a large number of soldier objects; a soldier object maintain the graphical representation of a soldier, soldier behavior such as motion, and firing weapons, in addition soldier’s health and location on the war terrain. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand.DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to defineCOMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through aADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance). OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.SINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object.PROXY PATTERN
The Proxy design pattern is applicable when there is a need to control access to an Object, as well as when there is a need for a sophisticated reference to an Object. Common Situations where the proxy pattern is applicable are: Virtual Proxies: delaying the creation and initialization of expensive objects until needed, wherethe objects are
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend of ABSTRACT FACTORY PATTERN Abstract Factory offers the interface for creating a family of related objects, without explicitly specifying their classes.Abstract Factory is a super-factory which creates other factories (Factory offactories).
FLYWEIGHT PATTERN
Flyweight Pattern Motivation. Some programs require a large number of objects that have some shared state among them. Consider for example a game of war, were there is a large number of soldier objects; a soldier object maintain the graphical representation of a soldier, soldier behavior such as motion, and firing weapons, in addition soldier’s health and location on the war terrain. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand.DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to defineCOMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through aADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance). OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.SINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object.PROXY PATTERN
The Proxy design pattern is applicable when there is a need to control access to an Object, as well as when there is a need for a sophisticated reference to an Object. Common Situations where the proxy pattern is applicable are: Virtual Proxies: delaying the creation and initialization of expensive objects until needed, wherethe objects are
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend of ABSTRACT FACTORY PATTERN Abstract Factory offers the interface for creating a family of related objects, without explicitly specifying their classes.Abstract Factory is a super-factory which creates other factories (Factory offactories).
FLYWEIGHT PATTERN
Flyweight Pattern Motivation. Some programs require a large number of objects that have some shared state among them. Consider for example a game of war, were there is a large number of soldier objects; a soldier object maintain the graphical representation of a soldier, soldier behavior such as motion, and firing weapons, in addition soldier’s health and location on the war terrain. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand.DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theFACTORY PATTERN
OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
ADAPTER PATTERN
INTERFACE SEGREGATION PRINCIPLE CHAIN OF RESPONSIBILITY PATTERNCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to defineCOMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through aADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance). OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.SINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object.PROXY PATTERN
The Proxy design pattern is applicable when there is a need to control access to an Object, as well as when there is a need for a sophisticated reference to an Object. Common Situations where the proxy pattern is applicable are: Virtual Proxies: delaying the creation and initialization of expensive objects until needed, wherethe objects are
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend of ABSTRACT FACTORY PATTERN Abstract Factory offers the interface for creating a family of related objects, without explicitly specifying their classes.Abstract Factory is a super-factory which creates other factories (Factory offactories).
FLYWEIGHT PATTERN
Flyweight Pattern Motivation. Some programs require a large number of objects that have some shared state among them. Consider for example a game of war, were there is a large number of soldier objects; a soldier object maintain the graphical representation of a soldier, soldier behavior such as motion, and firing weapons, in addition soldier’s health and location on the war terrain. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand.DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNFACTORY PATTERN
TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used.OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
COMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theVISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inSTRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNFACTORY PATTERN
TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used.OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
COMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theVISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
INTERFACE SEGREGATION PRINCIPLECREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to define TEMPLATE METHOD PATTERN Template Method Motivation If we take a look at the dictionary definition of a template we can see that a template is a preset format, used as a starting point for a particular application so that the format does not have to be recreated each time it is used.OBJECT POOL PATTERN
Intent - reuse and share objects that are expensive to create.ADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance).VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofDECORATOR PATTERN
Decorator Pattern Motivation. Extending an object’s functionality can be done statically (at compile time) by using inheritance however it might be necessary to extend an object’s functionality dynamically (at runtime) as an object is used.SINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object. ABSTRACT FACTORY PATTERN Abstract Factory offers the interface for creating a family of related objects, without explicitly specifying their classes.Abstract Factory is a super-factory which creates other factories (Factory offactories).
CHAIN OF RESPONSIBILITY PATTERN The Chain of Responsibility design pattern allows an object to send a command without knowing what object will receive and handle it. The request is sent from one object to another making them parts of a chain and each object in this chain can handle the command, pass it on or do both. The most usual example of a machine using the Chain of DEPENDENCY INVERSION PRINCIPLE Below is the code which supports the Dependency Inversion Principle. In this new design a new abstraction layer is added through the IWorker Interface. Now the problems from the above code are solved (considering there is no change in the high level logic): Manager class doesn't require changes when adding SuperWorkers.DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inFACTORY PATTERN
STRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theADAPTER PATTERN
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
INTERFACE SEGREGATION PRINCIPLE DEPENDENCY INVERSION PRINCIPLEDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inFACTORY PATTERN
STRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theADAPTER PATTERN
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
INTERFACE SEGREGATION PRINCIPLE DEPENDENCY INVERSION PRINCIPLEOBJECT POOL PATTERN
Intent - reuse and share objects that are expensive to create.ADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance).OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to define OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.COMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through aSINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand. LISKOV'S SUBSTITUTION PRINCIPLE Below is the classic example for which the Likov's Substitution Principle is violated. In the example 2 classes are used: Rectangle and Square. Let's assume that the Rectangle object is used somewhere in the application. We extend the application and add the Square class. The square class is returned by a factory pattern, based onsome
DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inFACTORY PATTERN
STRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theADAPTER PATTERN
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
INTERFACE SEGREGATION PRINCIPLE DEPENDENCY INVERSION PRINCIPLEDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inFACTORY PATTERN
STRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theADAPTER PATTERN
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
INTERFACE SEGREGATION PRINCIPLE DEPENDENCY INVERSION PRINCIPLEOBJECT POOL PATTERN
Intent - reuse and share objects that are expensive to create.ADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance).OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to define OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.COMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through aSINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand. LISKOV'S SUBSTITUTION PRINCIPLE Below is the classic example for which the Likov's Substitution Principle is violated. In the example 2 classes are used: Rectangle and Square. Let's assume that the Rectangle object is used somewhere in the application. We extend the application and add the Square class. The square class is returned by a factory pattern, based onsome
DESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inFACTORY PATTERN
STRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theADAPTER PATTERN
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
INTERFACE SEGREGATION PRINCIPLE DEPENDENCY INVERSION PRINCIPLEDESIGN PATTERNS
Design Patterns. By definition, Design Patterns are reusable solutions to commonly occuring problems (in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, inFACTORY PATTERN
STRATEGY PATTERN
Strategy Motivation There are common situations when classes differ only in their behavior. For this cases is a good idea to isolate the algorithms in separate classes in order to have the ability to select different algorithms at runtime. FACTORY METHOD PATTERNCOMMAND PATTERN
Command Pattern. “An object that contains a symbol, name or key that represents a list of commands, actions or keystrokes”. This is the definition of a macro, one that should be familiar to any computer user. From this idea the Command design pattern was given birth. The Macro represents, at some extent, a command that is built from theADAPTER PATTERN
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofFLYWEIGHT PATTERN
INTERFACE SEGREGATION PRINCIPLE DEPENDENCY INVERSION PRINCIPLEOBJECT POOL PATTERN
Intent - reuse and share objects that are expensive to create.ADAPTER PATTERN
Objects Adapters are the classical example of the adapter pattern. It uses composition, the Adaptee delegates the calls to Adaptee (opossed to class adapters which extends the Adaptee). This behaviour gives us a few advantages over the class adapters (however the class adapters can be implemented in languages allowing multiple inheritance).OBSERVER PATTERN
Model View Controller Pattern - The observer pattern is used in the model view controller (MVC) architectural pattern. In MVC the this pattern is used to decouple the model from the view. View represents the Observer and the model is the Observable object. Event management - This is one of the domains where the Observer patterns isextensively
VISITOR PATTERN
* The visitor pattern is a great way to provide a flexible design for adding new visitors to extend existing functionality without changing existing code * The Visitor pattern comes with a drawback: If a new visitable object is added to the framework structure all the implemented visitors need to be modified. The separation of visitors and visitable is only in one sense: visitors depend ofCREATIONAL PATTERNS
Structural Patterns ( 6 items ) Structural Patterns are the design patterns used to define structures of objects and classes that can work together and to define OPEN CLOSE PRINCIPLE The Open Close Principle(OCP) states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design should be done in a way to allow the adding of new functionality as new classes, keeping as much as possible existing code unchanged.COMPOSITE PATTERN
The composite pattern defines class hierarchies consisting of primitive objects and composite objects. Primitive objects can be composed into more complex objects, which in turn can be composed. Clients treat primitive and composite objects uniformly through aSINGLETON PATTERN
Singleton Design Pattern: Ensure that only one instance of a class is created; Provide a global point of access to the object. SINGLE RESPONSIBILITY PRINCIPLE The Single Responsibility Principle represents a good way of identifying classes during the design phase of an application and it reminds you to think of all the ways a class can evolve. A good separation of responsibilities is done only when the full picture of how the application should work is well understand. LISKOV'S SUBSTITUTION PRINCIPLE Below is the classic example for which the Likov's Substitution Principle is violated. In the example 2 classes are used: Rectangle and Square. Let's assume that the Rectangle object is used somewhere in the application. We extend the application and add the Square class. The square class is returned by a factory pattern, based onsome
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DESIGN PATTERNS
By definition, Design Patterns are reusable solutions to commonly occuring problems(in the context of software design). Design patterns were started as best practices that were applied again and again to similar problems encountered in different contexts. They become popular after they were collected, in a formalized form, in the Gang Of Four book in 1994. Originally published with c++ and smaltalk code samples, design patterns are very popular in Java and C# can be applied in all object oriented languanges. In functional languages like Scala, certain patterns are not necesary anymore. CREATIONAL DESIGN PATTERNS:Click to zoom
SINGLETON - Ensure
that only one instance of a class is created and Provide a global access point to the object. When to Use , Common Usage , Example: Lazy Singleton in Java,
Example: Early Singleton in Java Singleton pattern should be used when we must ensure that only one instance of a class is created and when the instance must be available through all the code. A special care should be taken in multi-threading environments when multiple threads must access the same resources through the same singleton object. There are many common situations when singleton pattern is used:- Logger Classes
- Configuration Classes - Accesing resources in shared mode - Other design patterns implemented as Singletons: Factories and Abstract Factories, Builder, PrototypeClick to zoom
FACTORY (Simplified
version of Factory Method) - Creates objects without exposing the instantiation logic to the client and Refers to the newly created object through a common interface. When to Use , Common Usage Factory pattern should be used when: - a framework delegate the creation of objects derived from a common superclass to the factory - we need flexibility in adding new types of objects that must be created by the class Along with singleton pattern the factory is one of the most used patterns. Almost any application has some factories. Here are a someexamples in java:
- factories providing an xml parser: javax.xml.parsers.DocumentBuilderFactory or javax.xml.parsers.SAXParserFactory - java.net.URLConnection - allows users to decide which protocol touse
Click to zoom
Document Application ExampleFACTORY METHOD
- Defines an interface for creating objects, but let subclasses to decide which class to instantiate and Refers to the newly created object through a common interface. When to Use , Common Usage Factory Method pattern should be used when: - a framework delegate the creation of objects derived from a common superclass to the factory - the base factory class does not know what concrete classes will be required to create - delegates to its subclasses the creation ofconcrete objects
- factory subclasses subclasses are aware of the concrete classes that must be instantiated Factory method pattern, compared to Factory pattern replace the factory with an abstract class and a set of concrete factories subclasses. The subclasses are responsible for creating concrete product objects; for factory method is possible adding new product classes without changing the abstract factory. The same result can be achieved for simplified factory pattern if reflection is used. Along with singleton pattern the factories are the most used patterns. Almost any application has some factories. Here are a someexamples:
- factories providing an xml parser: javax.xml.parsers.DocumentBuilderFactory or javax.xml.parsers.SAXParserFactoryClick to zoom
Look & Feel Example
ABSTRACT FACTORY
- Offers the
interface for creating a family of related objects, without explicitly specifying their classes. When to Use , Common Usage , Example: GuiLook & Feel in Java
Abstract Factory should be used when: * A system should be configured with one of multiple families ofproducts
* A system should be independent of how its products are created, composed and represented * Products from the same family should be used all together, products from different families ahould not be used togheter and this constraint must be ensured. * Only the product interfaces are revealed, the implementations remains hidden to the clients. Examples of abstract factories: * java.awt.Toolkit - the abstract superclass of all actual implementations of the Abstract Window Toolkit. Subclasses of Toolkit are used to bind the various components to particular native toolkit implementations(Java AWT). * javax.swing.LookAndFeel - an abstract swing factory to swithct between several look and feel for the components displayed(JavaSwing).
* java.sql.Connection - an abstract factory which create Statements, PreparedStatements, CallableStatements,... for each database flavor.Click to zoom
Text
Converter Example
BUILDER - Defines an instance for creating an object but letting subclasses decide which class to instantiate and Allows a finer control over the construction process. Example: Text Converter in JavaClick to zoom
PROTOTYPE - Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.Click to zoom
Database
Example
OBJECT POOL -
reuses and shares objects that are expensive to create.. When to Use , Common Usage , Sourcecode: Database Connection Pool in Java Basically, we'll use an object pool whenever there are several clients who needs the same stateless resource which is expensive tocreate.
The most common situations when object pool pattern is used: - Database Connections- Remote Objects
BEHAVIORAL DESIGN PATTERNS:Click to zoom
CHAIN OF RESPONSIBILIY- It
avoids attaching the sender of a request to its receiver, giving this way other objects the possibility of handling the request too. - The objects become parts of a chain and the request is sent from one object to another across the chain until one of the objects will handle it. Sourcecode:Click to zoom
Restaurant
Example
COMMAND - Encapsulate a request in an object, Allows the parameterization of clients with different requests and Allows saving the requests in a queue. Sourcecode: Buying/Selling stocks in JavaClick to zoom
INTERPRETER -
Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language / Map a domain to a language, the language to a grammar, and the grammar to a hierarchical object-oriented design Sourcecode: Romans Numerals Converter in JavaClick to zoom
ITERATOR - Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation. Sourcecode: Java IteratorClick to zoom
MEDIATOR - Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently. Sourcecode:Click to zoom
News
Publisher Example
OBSERVER - Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically. Sourcecode: News Publisher in JavaClick to zoom
Robot
Example
STRATEGY - Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it. Sourcecode: Robot Application in JavaClick to zoom
Travel Example
TEMPLATE METHOD
- Define the
skeleton of an algorithm in an operation, deferring some steps to subclasses / Template Method lets subclasses redefine certain steps of an algorithm without letting them to change the algorithm's structure. Sourcecode: Travel Agency Application in JavaClick to zoom
Customers
Example
VISITOR - Represents an operation to be performed on the elements of an object structure / Visitor lets you define a new operation without changing the classes of the elements on which it operates. Sourcecode: Customers ReportExample
Click to zoom
NULL OBJECT -
Provide an object as a surrogate for the lack of an object of a given type. / The Null Object Pattern provides intelligent do nothing behavior, hiding the details from its collaborators. Sourcecode: STRUCTURAL DESIGN PATTERNS:Click to zoom
ADAPTER - Convert the interface of a class into another interface clients expect. / Adapter lets classes work together, that could not otherwise because of incompatible interfaces.Click to zoom
Click to
zoom
BRIDGE - Compose
objects into tree structures to represent part-whole hierarchies. / Composite lets clients treat individual objects and compositions of objects uniformly. Sourcecode: Object Persistence Api in JavaClick to zoom
Shapes
Example
COMPOSITE - Compose objects into tree structures to represent part-whole hierarchies. / Composite lets clients treat individual objects and compositions of objects uniformly. Sourcecode: Shapes Example in JavaClick to zoom
GUI
Example
DECORATOR - add
additional responsibilities dynamically to an object. Sourcecode: GuiApplication Example
Click to zoom
Wargame Example
FLYWEIGHT - use
sharing to support a large number of objects that have part of their internal state in common where the other part of state can vary. Sourcecode: Java Wargame ExampleClick to zoom
Calculator
Example
MEMENTO - capture the internal state of an object without violating encapsulation and thus providing a mean for restoring the object into initial state when needed. Source Code: Calculator Example in JavaClick to zoom
Image Viewer
PROXY - provide a
“Placeholder” for an object to control references to it. Sourcecode: Proxy Pattern in JavaLoading...
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