Search results
Results from the WOW.Com Content Network
In object-oriented programming, the singleton pattern is a software design pattern that restricts the instantiation of a class to a singular instance. It is one of the well-known "Gang of Four" design patterns , which describe how to solve recurring problems in object-oriented software. [ 1 ]
Whereas the singleton allows only one instance of a class to be created, the multiton pattern allows for the controlled creation of multiple instances, which it manages through the use of a map. Rather than having a single instance per application (e.g. the java.lang.Runtime object in the Java programming language ) the multiton pattern instead ...
in Kotlin, Unit is a singleton with only one value: the Unit object. In Ruby, nil is the only instance of the NilClass class. In C++, the std::monostate unit type was added in C++17. Before that, it is possible to define a custom unit type using an empty struct such as struct empty{}.
This insulates client code from object creation by having clients request that a factory object create an object of the desired abstract type and return an abstract pointer to the object. [ 5 ] An example is an abstract factory class DocumentCreator that provides interfaces to create a number of products (e.g., createLetter() and createResume() ).
Design Patterns: Elements of Reusable Object-Oriented Software (1994) is a software engineering book describing software design patterns.The book was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, with a foreword by Grady Booch.
The initialization of the LazyHolder class results in static variable INSTANCE being initialized by executing the (private) constructor for the outer class Something. Since the class initialization phase is guaranteed by the JLS to be sequential, i.e., non-concurrent, no further synchronization is required in the static getInstance method ...
A set of related objects is designed to be used together. Hiding the implementations of a class library or product, revealing only their interfaces. Constructing different representation of independent complex objects. A class wants its subclass to implement the object it creates. The class instantiations are specified at run-time.
It should be possible to define a new operation for (some) classes of an object structure without changing the classes. When new operations are needed frequently and the object structure consists of many unrelated classes, it's inflexible to add new subclasses each time a new operation is required because "[..] distributing all these operations across the various node classes leads to a system ...