Search results
Results From The WOW.Com Content Network
Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
In that case a new object B is created, and the fields values of A are copied over to B. [3] [4] [5] This is also known as a field-by-field copy, [6] [7] [8] field-for-field copy, or field copy. [9] If the field value is a reference to an object (e.g., a memory address) it copies the reference, hence referring to the same object as A does, and ...
An object reference means a name, and the passed reference is an "alias", i.e. a copy of the reference to the same object, just as in C/C++. The object's value may be changed in the called function with the "alias", for example:
In computer science, having value semantics (also value-type semantics or copy-by-value semantics) means for an object that only its value counts, not its identity. [1] [2] Immutable objects have value semantics trivially, [3] and in the presence of mutation, an object with value semantics can only be uniquely-referenced at any point in a program.
Using this technique, when a user asks the system to copy an object, it instead merely creates a new reference that still points to the same object. As soon as a user attempts to modify the object through a particular reference, the system makes a real copy, applies the modification to that, and sets the reference to refer to the new copy.
Another complication with this approach is that, in languages with both reference types and unboxed value types, the garbage collector needs to somehow be able to distinguish which variables on the stack or fields in an object are regular values and which are references: in memory, an integer and a reference might look alike. The garbage ...
Call by reference (or pass by reference) is an evaluation strategy where a parameter is bound to an implicit reference to the variable used as argument, rather than a copy of its value. This typically means that the function can modify (i.e., assign to ) the variable used as argument—something that will be seen by its caller.
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 ...