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Decorator Pattern
In object-oriented programming, the decorator pattern is a design pattern that allows behavior to be added to an individual object, dynamically, without affecting the behavior of other instances of the same class. The decorator pattern is often useful for adhering to the Single Responsibility Principle, as it allows functionality to be divided between classes with unique areas of concern as well as to the Open-Closed Principle, by allowing the functionality of a class to be extended without being modified. Decorator use can be more efficient than subclassing, because an object's behavior can be augmented without defining an entirely new object. Overview The ''decorator'' design pattern is one of the twenty-three well-known ''design patterns''; these describe how to solve recurring design problems and design flexible and reusable object-oriented software—that is, objects which are easier to implement, change, test, and reuse. The decorator pattern provides a flexible alterna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Python Syntax And Semantics
The syntax of the Python programming language is the set of rules that defines how a Python program will be written and interpreted (by both the runtime system and by human readers). The Python language has many similarities to Perl, C, and Java. However, there are some definite differences between the languages. It supports multiple programming paradigms, including structured, object-oriented programming, and functional programming, and boasts a dynamic type system and automatic memory management. Python's syntax is simple and consistent, adhering to the principle that "There should be one— and preferably only one —obvious way to do it." The language incorporates built-in data types and structures, control flow mechanisms, first-class functions, and modules for better code reusability and organization. Python also uses English keywords where other languages use punctuation, contributing to its uncluttered visual layout. The language provides robust error handling thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java Platform, Standard Edition
Java Platform, Standard Edition (Java SE) is a computing platform for development and deployment of porting, portable code for desktop computer, desktop and server (computing), server environments. Java SE was formerly known as Java 2 Platform, Standard Edition (J2SE). The platform uses the Java (programming language), Java programming language and is part of the Java (software platform), Java software-platform family. Java SE defines a range of general-purpose APIs—such as List of Java APIs, Java APIs for the Java Class Library—and also includes the Java Language Specification and the Java Virtual Machine Specification. OpenJDK is the official reference implementation since version 7. Nomenclature, standards and specifications The platform was known as ''Java 2 Platform, Standard Edition'' or ''J2SE'' from version 1.2, until the name was changed to ''Java Platform, Standard Edition'' or ''Java SE'' in version 1.5. The "SE" is used to distinguish the base platform from th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adapter Pattern
In software engineering, the adapter pattern is a software design pattern (also known as wrapper, an alternative naming shared with the decorator pattern) that allows the interface of an existing class to be used as another interface. It is often used to make existing classes work with others without modifying their source code. An example is an adapter that converts the interface of a Document Object Model of an XML document into a tree structure that can be displayed. Overview The adapter design pattern is one of the twenty-three well-known Gang of Four design patterns that describe how to solve recurring design problems to design flexible and reusable object-oriented software, that is, objects that are easier to implement, change, test, and reuse. The adapter design pattern solves problems like: * How can a class be reused that does not have an interface that a client requires? * How can classes that have incompatible interfaces work together? * How can an alternative inte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facade Pattern
The facade pattern (also spelled ''façade'') is a software design pattern commonly used in object-oriented programming. Analogous to a façade in architecture, it is an object that serves as a front-facing interface masking more complex underlying or structural code. A facade can: * improve the readability and usability of a software library by masking interaction with more complex components behind a single (and often simplified) application programming interface (API) * provide a context-specific interface to more generic functionality (complete with context-specific input validation) * serve as a launching point for a broader refactor of monolithic or tightly-coupled systems in favor of more loosely-coupled code Developers often use the facade design pattern when a system is very complex or difficult to understand because the system has many interdependent classes or because its source code is unavailable. This pattern hides the complexities of the larger system and provides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Composition Over Inheritance
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor Polymorphism (computer science), polymorphic behavior and code reuse by their object composition, composition (by containing instances of other classes that implement the desired functionality) over Inheritance (computer science), inheritance from a base or parent class. Ideally all reuse can be achieved by assembling existing components, but in practice inheritance is often needed to make new ones. Therefore inheritance and object composition typically work hand-in-hand, as discussed in the book ''Design Patterns'' (1994). Basics An implementation of composition over inheritance typically begins with the creation of various Interface (computing)#In object-oriented languages, interfaces representing the behaviors that the system must exhibit. Interfaces can facilitate Polymorphism (computer science), polymorphic behavior. Classes implementing t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visitor Pattern
A visitor pattern is a software design pattern that separates the algorithm from the object structure. Because of this separation, new operations can be added to existing object structures without modifying the structures. It is one way to follow the open/closed principle in object-oriented programming and software engineering. In essence, the visitor allows adding new virtual functions to a family of classes, without modifying the classes. Instead, a visitor class is created that implements all of the appropriate specializations of the virtual function. The visitor takes the instance reference as input, and implements the goal through double dispatch. Programming languages with sum types and pattern matching obviate many of the benefits of the visitor pattern, as the visitor class is able to both easily branch on the type of the object and generate a compiler error if a new object type is defined which the visitor does not yet handle. Overview The Visitor design pattern i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adapter Pattern
In software engineering, the adapter pattern is a software design pattern (also known as wrapper, an alternative naming shared with the decorator pattern) that allows the interface of an existing class to be used as another interface. It is often used to make existing classes work with others without modifying their source code. An example is an adapter that converts the interface of a Document Object Model of an XML document into a tree structure that can be displayed. Overview The adapter design pattern is one of the twenty-three well-known Gang of Four design patterns that describe how to solve recurring design problems to design flexible and reusable object-oriented software, that is, objects that are easier to implement, change, test, and reuse. The adapter design pattern solves problems like: * How can a class be reused that does not have an interface that a client requires? * How can classes that have incompatible interfaces work together? * How can an alternative inte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flyweight Pattern
In computer programming, the flyweight software design pattern refers to an Object (computer science), object that minimizes Computer memory, memory usage by sharing some of its data with other similar objects. The flyweight pattern is one of twenty-three well-known ''Design Patterns, GoF design patterns''. These patterns promote flexible object-oriented software design, which is easier to implement, change, test, and reuse. In other contexts, the idea of sharing data structures is called hash consing. The term was first coined, and the idea extensively explored, by Paul Calder and Mark Linton in 1990 to efficiently handle glyph information in a WYSIWYG, WYSIWYG document editor. Similar techniques were already used in other systems, however, as early as 1988. Overview The flyweight pattern is useful when dealing with a large number of objects that share simple repeated elements which would use a large amount of memory if they were individually embedded. It is common to hold sha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
State Pattern
The state pattern is a Behavioral pattern, behavioral software design pattern that allows an object to alter its behavior when its internal state changes. This pattern is close to the concept of finite-state machines. The state pattern can be interpreted as a strategy pattern, which is able to switch a strategy through invocations of methods defined in the pattern's interface. The state pattern is used in computer programming to encapsulate varying behavior for the same object (computer science), object, based on its internal state. This can be a cleaner way for an object to change its behavior at runtime without resorting to conditional statements and thus improve maintainability. Overview The state design pattern is one of twenty-three Design Patterns, design patterns documented by the Gang of Four that describe how to solve recurring design problems. Such problems cover the design of flexible and reusable object-oriented software, such as objects that are easy to implement, cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Command Pattern
In object-oriented programming, the command pattern is a Behavioral pattern, behavioral Design pattern (computer science), design pattern in which an object is used to Information hiding, encapsulate all information needed to perform an action or trigger an event at a later time. This information includes the method name, the object that owns the method and values for the method parameters. Four terms always associated with the command pattern are ''command'', ''receiver'', ''invoker'' and ''client''. A ''command'' object knows about ''receiver'' and invokes a method of the receiver. Values for parameters of the receiver method are stored in the command. The receiver object to execute these methods is also stored in the command object by Object composition#Aggregation, aggregation. The ''receiver'' then does the work when the execute() method in ''command'' is called. An ''invoker'' object knows how to execute a command, and optionally does bookkeeping about the command execution. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scrollbar
A scrollbar is an interaction technique or widget (GUI), widget in which continuous text, pictures, or any other content can be Scrolling, scrolled in a predetermined direction (up, down, left, or right) on a computer display, window (computing), window, or viewport so that all of the content can be viewed, even if only a fraction of the content can be seen on a device's screen at one time. It offers a solution to the problem of Web navigation, navigation to a known or unknown location within a two-dimensional information space. It was also known as a handle in the very first GUIs. They are present in a wide range of electronic devices including computers, graphing calculators, mobile phones, and portable media players. The user interacts with the scrollbar elements using some method of direct action, the scrollbar translates that action into scrolling commands, and the user receives feedback through a visual updating of both the scrollbar elements and the scrolled content. Altho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scrolling
In computer displays, filmmaking, television production, video games and other kinetic displays, scrolling is sliding text, images or video across a monitor or display, vertically or horizontally. "Scrolling," as such, does not change the layout of the text or pictures but moves ( pans or tilts) the user's view across what is apparently a larger image that is not wholly seen. A common television and movie special effect is to scroll credits, while leaving the background stationary. Scrolling may take place completely without user intervention (as in film credits) or, on an interactive device, be triggered by touchscreen or a keypress and continue without further intervention until a further user action, or be entirely controlled by input devices. Scrolling may take place in discrete increments (perhaps one or a few lines of text at a time), or continuously (smooth scrolling). Frame rate is the speed at which an entire image is redisplayed. It is related to scrolling in that chan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
