Check out our ebook on design patterns and principles. It's available in PDF/ePUB/MOBI formats and includes the archive with code examples in Java, C#, C, PHP, Python, Ruby, Go, Swift, & TypeScript. The Design Patterns PDF is a nice resource, congratulations on putting it together. Here are a few refinements you may wish to consider: 1) Optional (blank) compartments do not need to be represents as you have represented in your Memento and Observer patterns for operations. 2) Class names do not have spaces. Design Patterns Java Cheat Sheet Pdf.
This design patterns refcard provides a quick reference to the original 23 gang of four design patterns as listed in the book design patterns. Software design patterns and methodology cheat sheet ratings. Strategy lets the algorithm vary independently from clients who use it. The 23 gang of four design patterns cheat sheet 1. Pingback: Designs patterns, Cheat Sheet « Java Village. Madhu Gumma says: October 16, 2008 at 12:16 pm. Pingback: Design Patterns Cheat Sheet at building blocks. Core Java Cheat Sheet Java is an open source programming language that has been changing the face of the IT market since ages. It is widely preferred by the programmers as the code written in Java can be executed securely on any platform, irrespective of the operating system or architecture of the device.
Some time ago, I read a free book covering some of the design patterns in JavaScript. I found myself referring back to it from time to time. Here is the notes I took listed here to make a quick reference cheat sheet:
Problem to solve:
Often a class or object will contain other objects within it. The logic of creating objects lives inside the parent object and creates a dependency between the child class and parent class
Simple Factory Pattern:
Description:
Uses a separate class (often a singleton) to create instances
Example:
CarFactory::createCar(model) => Car
Complex Factory Pattern:
Description:
Uses subclasses to decide what concrete class to instantiate as a member object.
Example:
AbstractBaseFactory::createCar(model)
AWDFactory::createCar(model) => awdModelCar
SedanFactory::createCar(model) => sedanModelCar
Problem to solve:
decouple an abstraction from its implementation so that the two can vary independently.
Example 1: Event Handler
getBeerById(id, callback)
addEvent(element, ‘click’, function(e){ getBeerById(e.id, cb) );
instead of
addEvent(element, ‘click’, getBeerById(e) { … }); //couples the implementation with event
Example 2: Privileged methods as a bridge to gain access to the private variable
Example 3: Bridging Multiple Classes Together
Problems to solve:
To treat a collection of objects the same as you would treat any of the particular sub-objects. It organizes sub-objects into a tree structure and allows the entire tree to be traversed.
Examples:
Form validation
Forms – >validate()
Form -> validate()
Section -> validate()
Field -> validate()
Hide/Show HTML Elements
parentDiv -> hide/show
childrenDiv -> hide/show
element -> hide/show
Problem to solve:
The facade pattern does two things:
- it simplifies the interface of a class,
- and it decouples that class from the client code that uses it.
Example: Create a function for registering event handler in all browsers
Example: As Convenient Methods
Problem to solve:
The adapter pattern allows you to adapt existing interfaces to classes that would otherwise be incompatible.
What it is
An adapter converts one interface to another; it doesn’t remove any ability or otherwise simplify the interface.
Note that Adapter class simply wraps an object and converts the arguments given into what the function expects to receive.
The problem to solve:
The decorator pattern is used to transparently wrap objects within another object of the same interface. This allows you to add behavior to a method and then pass the method call on to the original object. Using decorator objects is a flexible alternative to creating subclasses.
In What Ways Can a Decorator Modify Its Component?
- Adding Behavior Before/After a Method
- Replacing a Method
- Adding New Methods
The problem to solve:
It’s most useful in situations where large numbers of similar objects are created, causing performance problems.
The flyweight pattern is used to reduce the number of objects you need in your applications.
How
The first step is to separate the intrinsic state (information that is required by the internal methods of a class e.g. car make/model/year/) from the extrinsic state (information that can be removed from a class and stored externally e.g. owner details).
Instantiation Using a Factory ( make sure only one object is created for each intrinsic state )
Extrinsic State Encapsulated (e.g. a collection/database/composite of owners ) in a singleton Manager (e.g. car registration manager )
Examples:
- Tooltips and Tooltip manager
- Modals and Modal manager
A proxy is an object that can be used to control access to another object. It implements the same interface as this other object and passes on any method invocations to it.
A proxy does not modify the method calls that are passed on to the
real subject, other than to possibly add some control code.
Example:
- A virtual proxy controls access to a real subject that is expensive to create. It will defer instantiation of its real subject until a method is called
A remote proxy is used to access an object in a different environment.
A protection proxy is used to control access to certain methods based on who the client is.
Problem to solve:
Observe the state of an object in a program and be notified when it changes.
A observable object has three methods associated with the instance:
subscribe, unSubscribe, and fire
It provides the ability to parameterize and pass around a method call, which can then be executed whenever you need it to be.
It provides the ability to parameterize and pass around a method call, which can then be executed whenever you need it to be.
Example: Undo and Logging
To decouple the sender and the receiver of a request
Example: Express Middleware
Some time ago, I read a free book covering some of the design patterns in JavaScript. I found myself referring back to it from time to time. Here is the notes I took listed here to make a quick reference cheat sheet:
Problem to solve:
Often a class or object will contain other objects within it. The logic of creating objects lives inside the parent object and creates a dependency between the child class and parent class
Simple Factory Pattern:
Description:
Uses a separate class (often a singleton) to create instances
Example:
CarFactory::createCar(model) => Car
Complex Factory Pattern:
Description:
Uses subclasses to decide what concrete class to instantiate as a member object.
Example:
AbstractBaseFactory::createCar(model)
AWDFactory::createCar(model) => awdModelCar
SedanFactory::createCar(model) => sedanModelCar
Problem to solve:
decouple an abstraction from its implementation so that the two can vary independently.
Example 1: Event Handler
getBeerById(id, callback)
addEvent(element, ‘click’, function(e){ getBeerById(e.id, cb) );
instead of
addEvent(element, ‘click’, getBeerById(e) { … }); //couples the implementation with event
Example 2: Privileged methods as a bridge to gain access to the private variable
Example 3: Bridging Multiple Classes Together
Problems to solve:
To treat a collection of objects the same as you would treat any of the particular sub-objects. It organizes sub-objects into a tree structure and allows the entire tree to be traversed.
Examples:
Form validation
Forms – >validate()
Form -> validate()
Section -> validate()
Field -> validate()
Hide/Show HTML Elements
parentDiv -> hide/show
childrenDiv -> hide/show
element -> hide/show
Problem to solve:
The facade pattern does two things:
- it simplifies the interface of a class,
- and it decouples that class from the client code that uses it.
Example: Create a function for registering event handler in all browsers
Example: As Convenient Methods
Problem to solve:
The adapter pattern allows you to adapt existing interfaces to classes that would otherwise be incompatible.
What it is
An adapter converts one interface to another; it doesn’t remove any ability or otherwise simplify the interface.
Note that Adapter class simply wraps an object and converts the arguments given into what the function expects to receive.
The problem to solve:
The decorator pattern is used to transparently wrap objects within another object of the same interface. This allows you to add behavior to a method and then pass the method call on to the original object. Using decorator objects is a flexible alternative to creating subclasses.
In What Ways Can a Decorator Modify Its Component?
- Adding Behavior Before/After a Method
- Replacing a Method
- Adding New Methods
The problem to solve:
It’s most useful in situations where large numbers of similar objects are created, causing performance problems.
The flyweight pattern is used to reduce the number of objects you need in your applications.
How
The first step is to separate the intrinsic state (information that is required by the internal methods of a class e.g. car make/model/year/) from the extrinsic state (information that can be removed from a class and stored externally e.g. owner details).
Instantiation Using a Factory ( make sure only one object is created for each intrinsic state )
Extrinsic State Encapsulated (e.g. a collection/database/composite of owners ) in a singleton Manager (e.g. car registration manager )
Java Design Patterns Cheat Sheet
Examples:
- Tooltips and Tooltip manager
- Modals and Modal manager
A proxy is an object that can be used to control access to another object. It implements the same interface as this other object and passes on any method invocations to it.
Design Patterns In Java Cheat Sheet
A proxy does not modify the method calls that are passed on to the
real subject, other than to possibly add some control code.
Example:
- A virtual proxy controls access to a real subject that is expensive to create. It will defer instantiation of its real subject until a method is called
A remote proxy is used to access an object in a different environment.
A protection proxy is used to control access to certain methods based on who the client is.
Problem to solve:
Observe the state of an object in a program and be notified when it changes.
A observable object has three methods associated with the instance:
subscribe, unSubscribe, and fire
It provides the ability to parameterize and pass around a method call, which can then be executed whenever you need it to be.
It provides the ability to parameterize and pass around a method call, which can then be executed whenever you need it to be.
Example: Undo and Logging
To decouple the sender and the receiver of a request
Design Patterns C# Pdf
Example: Express Middleware