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In computer programming, operator overloading, sometimes termed operator ad hoc polymorphism, is a specific case of polymorphism, where different operators have different implementations depending on their arguments. Operator overloading is generally defined by a programming language, a programmer, or both.
When not overloaded, for the operators &&, ||, and , (the comma operator), there is a sequence point after the evaluation of the first operand. Most of the operators available in C and C++ are also available in other C-family languages such as C# , D , Java , Perl , and PHP with the same precedence, associativity, and semantics.
The new operator can be overloaded so that specific types (classes) use custom memory allocation algorithms for their instances. For example, the following is a variant of the singleton pattern where the first new Singleton call allocates an instance and all subsequent calls return this same instance:
The previous section notwithstanding, there are other ways in which ad hoc polymorphism can work out. Consider for example the Smalltalk language. In Smalltalk, the overloading is done at run time, as the methods ("function implementation") for each overloaded message ("overloaded function") are resolved when they are about to be executed.
In computer programming, an operator is a programming language construct that provides functionality that may not be possible to define as a user-defined function (i.e. sizeof in C) or has syntax different than a function (i.e. infix addition as in a+b). Some languages allow a language-defined operator to be overridden with user-defined ...
Overloading an operator does not change the precedence of calculations involving the operator, nor does it change the number of operands that the operator uses (any operand may however be ignored by the operator, though it will be evaluated prior to execution). Overloaded "&&" and "||" operators lose their short-circuit evaluation property.
However, there is no delete operator due to garbage collection mechanisms in Java, and there are no operations on pointers since Java does not support them. Another difference is that Java has an unsigned right shift operator (>>>), while C's right shift operator's signedness is type-dependent. Operators in Java cannot be overloaded.
Assignment operators (+=, *= etc.) are combinations of a binary operator and the assignment operator (=) and will be evaluated using the ordinary operators, which can be overloaded. Cast operators ( ( ) ) cannot be overloaded, but it is possible to define conversion operators.