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In object-oriented programming, the iterator pattern is a design pattern in which an iterator is used to traverse a container and access the container's elements. The iterator pattern decouples algorithms from containers; in some cases, algorithms are necessarily container-specific and thus cannot be decoupled.
An example of generalizing a type would be moving a method from a child to a parent class for common use by all the parent class' children, not just the original child. Another example, in the Java programming language , would be access to an object via an interface which isn't tied into a specific implementation of that interface.
Refactoring is usually motivated by noticing a code smell. [2] For example, the method at hand may be very long, or it may be a near duplicate of another nearby method. Once recognized, such problems can be addressed by refactoring the source code, or transforming it into a new form that behaves the same as before but that no longer "smells".
The latest Java BluePrints offering is the Java BluePrints Solutions Catalog. [3] It covers topics as diverse as Java Server Faces, Web Services, and Asynchronous Javascript and XML ( Ajax ). Articles are smaller and more focused and include sample code that shows how a solution is implemented.
Sample Code: An illustration of how the pattern can be used in a programming language. Known Uses: Examples of real usages of the pattern. Related Patterns: Other patterns that have some relationship with the pattern; discussion of the differences between the pattern and similar patterns.
The factory method design pattern solves problems such as: How can an object's subclasses redefine its subsequent and distinct implementation? The pattern involves creation of a factory method within the superclass that defers the object's creation to a subclass's factory method.
It states that two instances of similar code do not require refactoring, but when similar code is used three times, it should be extracted into a new procedure. The rule was popularised by Martin Fowler in Refactoring [1] and attributed to Don Roberts. Duplication is considered a bad practice in programming because it makes the code harder to ...
A sample UML class and sequence diagram for the observer design pattern. [6] In this UML class diagram, the Subject class does not update the state of dependent objects directly. Instead, Subject refers to the Observer interface (update()) for updating state, which makes the Subject independent of how the state of dependent objects is updated.