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In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
An object-oriented structural design pattern for organizing objects in loosely typed key-value stores and exposing the data using typed views. The purpose of the pattern is to achieve a high degree of flexibility between components in a strongly typed language where new properties can be added to the object-tree on the fly, without losing the support of type-safety.
Nullable types are a feature of some programming languages which allow a value to be set to the special value NULL instead of the usual possible values of the data type.In statically typed languages, a nullable type is an option type, [citation needed] while in dynamically typed languages (where values have types, but variables do not), equivalent behavior is provided by having a single null ...
C# has and allows pointers to selected types (some primitives, enums, strings, pointers, and even arrays and structs if they contain only types that can be pointed [14]) in unsafe context: methods and codeblock marked unsafe. These are syntactically the same as pointers in C and C++.
For function that manipulate strings, modern object-oriented languages, like C# and Java have immutable strings and return a copy (in newly allocated dynamic memory), while others, like C manipulate the original string unless the programmer copies data to a new string. See for example Concatenation below.
The original form of the pattern, appearing in Pattern Languages of Program Design 3, [2] has data races, depending on the memory model in use, and it is hard to get right. Some consider it to be an anti-pattern. [3] There are valid forms of the pattern, including the use of the volatile keyword in Java and explicit memory barriers in C++. [4]
Once objects populate the cache, the object retrieval algorithm might have more overhead associated than the push/pop operations of a maintained cache. When retrieving extrinsic objects with immutable state one must simply search the cache for an object with the state one desires. If no such object is found, one with that state must be initialized.
The adapter [2] 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: [3]