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Non-virtual Interface Pattern
The non-virtual interface pattern (NVI) controls how methods in a base class are overridden. Such methods may be called by clients and overridable methods with core functionality. It is a pattern that is strongly related to the template method pattern. The NVI pattern recognizes the benefits of a non-abstract method invoking the subordinate abstract methods. This level of indirection allows for pre and post operations relative to the abstract operations both immediately and with future unforeseen changes. The NVI pattern can be deployed with very little software production and runtime cost. Many commercial software frameworks employ the NVI pattern. Benefits and detriments A design that adheres to this pattern results in a separation of a class interface into two distinct interfaces: # Client interface: This is the public non-virtual interface # Subclass interface: This is the private interface, which can have any combination virtual and non-virtual methods. With such a structure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Design Pattern (computer Science)
In software engineering, a software design pattern is a general, reusable solution to a commonly occurring problem within a given context in software design. It is not a finished design that can be transformed directly into source or machine code. Rather, it is a description or template for how to solve a problem that can be used in many different situations. Design patterns are formalized best practices that the programmer can use to solve common problems when designing an application or system. Object-oriented design patterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved. Patterns that imply mutable state may be unsuited for functional programming languages. Some patterns can be rendered unnecessary in languages that have built-in support for solving the problem they are trying to solve, and object-oriented patterns are not necessarily suitable for non-object-oriented langua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Class
In object-oriented programming, inheritance is the mechanism of basing an object or class upon another object ( prototype-based inheritance) or class ( class-based inheritance), retaining similar implementation. Also defined as deriving new classes ( sub classes) from existing ones such as super class or base class and then forming them into a hierarchy of classes. In most class-based object-oriented languages, an object created through inheritance, a "child object", acquires all the properties and behaviors of the "parent object" , with the exception of: constructors, destructor, overloaded operators and friend functions of the base class. Inheritance allows programmers to create classes that are built upon existing classes, to specify a new implementation while maintaining the same behaviors ( realizing an interface), to reuse code and to independently extend original software via public classes and interfaces. The relationships of objects or classes through inheritance give ris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Template Method Pattern
In object-oriented programming, the template method is one of the behavioral design patterns identified by Gamma et al. in the book ''Design Patterns''. The template method is a method in a superclass, usually an abstract superclass, and defines the skeleton of an operation in terms of a number of high-level steps. These steps are themselves implemented by additional ''helper methods'' in the same class as the ''template method''. The ''helper methods'' may be either ''abstract methods'', in which case subclasses are required to provide concrete implementations, or '' hook methods,'' which have empty bodies in the superclass. Subclasses can (but are not required to) customize the operation by overriding the hook methods. The intent of the template method is to define the overall structure of the operation, while allowing subclasses to refine, or redefine, certain steps. Overview This pattern has two main parts: * The "template method" is implemented as a method in a base c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fragile Base Class
The fragile base class problem is a fundamental architectural problem of object-oriented programming systems where base classes ( superclasses) are considered "fragile" because seemingly safe modifications to a base class, when inherited by the derived classes, may cause the derived classes to malfunction. The programmer cannot determine whether a base class change is safe simply by examining in isolation the methods of the base class. One possible solution is to make instance variables private to their defining class and force subclasses to use accessors to modify superclass states. A language could also make it so that subclasses can control which inherited methods are exposed publicly. These changes prevent subclasses from relying on implementation details of superclasses and allow subclasses to expose only those superclass methods that are applicable to themselves. Another alternative solution could be to have an interface instead of superclass. The fragile base class probl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Template Method Pattern
In object-oriented programming, the template method is one of the behavioral design patterns identified by Gamma et al. in the book ''Design Patterns''. The template method is a method in a superclass, usually an abstract superclass, and defines the skeleton of an operation in terms of a number of high-level steps. These steps are themselves implemented by additional ''helper methods'' in the same class as the ''template method''. The ''helper methods'' may be either ''abstract methods'', in which case subclasses are required to provide concrete implementations, or '' hook methods,'' which have empty bodies in the superclass. Subclasses can (but are not required to) customize the operation by overriding the hook methods. The intent of the template method is to define the overall structure of the operation, while allowing subclasses to refine, or redefine, certain steps. Overview This pattern has two main parts: * The "template method" is implemented as a method in a base c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Design Patterns
In software engineering, a software design pattern is a general, reusable solution to a commonly occurring problem within a given context in software design. It is not a finished design that can be transformed directly into source or machine code. Rather, it is a description or template for how to solve a problem that can be used in many different situations. Design patterns are formalized best practices that the programmer can use to solve common problems when designing an application or system. Object-oriented design patterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved. Patterns that imply mutable state may be unsuited for functional programming languages. Some patterns can be rendered unnecessary in languages that have built-in support for solving the problem they are trying to solve, and object-oriented patterns are not necessarily suitable for non-object-oriented langua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Articles With Example Java Code
Article often refers to: * Article (grammar), a grammatical element used to indicate definiteness or indefiniteness * Article (publishing), a piece of nonfictional prose that is an independent part of a publication Article may also refer to: Government and law * Article (European Union), articles of treaties of the European Union * Articles of association, the regulations governing a company, used in India, the UK and other countries * Articles of clerkship, the contract accepted to become an articled clerk * Articles of Confederation, the predecessor to the current United States Constitution *Article of Impeachment, a formal document and charge used for impeachment in the United States * Articles of incorporation, for corporations, U.S. equivalent of articles of association * Articles of organization, for limited liability organizations, a U.S. equivalent of articles of association Other uses * Article, an HTML element, delimited by the tags and * Article of clothing, an ite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
