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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".
In object-oriented languages, access to objects is achieved through references (or, equivalently, pointers). A typical call is of the form: x.f(a, ...) where f denotes an operation and x denotes a reference to some object. At execution time, however, a reference can be void (or null).
In computing, a null pointer or null reference is a value saved for indicating that the pointer or reference does not refer to a valid object. Programs routinely use null pointers to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types ...
The language does not provide any explicit pointer manipulation operators. It is still possible for code to attempt to dereference a null reference (null pointer), however, which results in a run-time exception being thrown. The space occupied by unreferenced memory objects is recovered automatically by garbage collection at run-time. [20]
In object-oriented programming, the safe navigation operator (also known as optional chaining operator, safe call operator, null-conditional operator, null-propagation operator) is a binary operator that returns null if its first argument is null; otherwise it performs a dereferencing operation as specified by the second argument (typically an ...
In computer programming, a weak reference is a reference that does not protect the referenced object from collection by a garbage collector, unlike a strong reference.An object referenced only by weak references – meaning "every chain of references that reaches the object includes at least one weak reference as a link" – is considered weakly reachable, and can be treated as unreachable and ...
In JavaScript, there are 7 primitive data types: string, number, bigint, boolean, symbol, undefined, and null. [19] Their values are considered immutable. These are not objects and have no methods or properties; however, all primitives except undefined and null have object wrappers. [20]
load onto the stack a reference from an array aastore 53 0101 0011 arrayref, index, value → store a reference in an array aconst_null 01 0000 0001 → null push a null reference onto the stack aload 19 0001 1001 1: index → objectref load a reference onto the stack from a local variable #index: aload_0 2a 0010 1010 → objectref