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2025-06-19T14:17:38Z

"?:": ?: does not appear in most programming languages

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{{Wiktionary|conditional operator}}

{{mergeto|ternary conditional operator|discuss=Talk:Conditional operator#Related Article|date=February 2025}}

The '''conditional operator''' is supported in many [[programming language]]s. This term usually refers to <code>?:</code> as in [[C (programming language)|C]], [[C++]], [[C sharp (programming language)|C#]], [[JavaScript]] and [[PHP]]. However, in Java, this term can also refer to <code>&&</code> and <code>||</code>.

== && and || ==
In some programming languages, e.g. Java, the term ''conditional operator'' refers to [[Short-circuit evaluation|short circuit boolean operators]] <code>&&</code> and <code>||</code>. The second expression is evaluated only when the first expression is not sufficient to determine the value of the whole expression.<ref>{{Cite web|url=https://docs.oracle.com/javase/tutorial/java/nutsandbolts/op2.html|title=Equality, Relational, and Conditional Operators (The Java™ Tutorials > Learning the Java Language > Language Basics)|website=docs.oracle.com|access-date=2019-04-29}}</ref>

=== Difference from bitwise operator ===
<code>&</code> and <code>|</code> are [[Bitwise operation|bitwise operators]] that occur in many programming languages. The major difference is that bitwise operations operate on the individual bits of a binary numeral, whereas conditional operators operate on logical operations. Additionally, expressions before and after a bitwise operator are always evaluated.
<syntaxhighlight lang="java">
if (expression1 || expression2 || expression3)

</syntaxhighlight>If expression 1 is true, expressions 2 and 3 are NOT checked.
<syntaxhighlight lang="java">
if (expression1 | expression2 | expression3)
</syntaxhighlight>This checks expressions 2 and 3, even if expression 1 is true.

Short circuit operators can reduce run times by avoiding unnecessary calculations. They can also avoid Null Exceptions when expression 1 checks whether an object is valid.

=== Usage in Java ===
<syntaxhighlight lang="java">
class ConditionalDemo1 {

public static void main(String[] args) {
int value1 = 1;
int value2 = 2;
if ((value1 == 1) && (value2 == 2))
System.out.println("value1 is 1 AND value2 is 2");
if ((value1 == 1) || (value2 == 1))
System.out.println("value1 is 1 OR value2 is 1");
}
}

</syntaxhighlight>

== "?:" ==
In some programming languages, [[?:]] is called the conditional operator. It is a type of [[ternary operator]]. However, ternary operator in most situations refers specifically to [[?:]] because it is the only operator that takes three operands.<ref name=":0">{{Cite web|url=https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/conditional-operator|title=?: Operator - C# Reference|last=BillWagner|website=docs.microsoft.com|language=en-us|access-date=2019-04-29}}</ref>

=== Regular usage of "?:" ===
<code>?:</code> is used in conditional expressions. Programmers can rewrite an if-then-else expression in a more concise way by using the conditional operator.<ref>{{Cite web|url=http://www.cafeaulait.org/course/week2/43.html|title=The ? : operator in Java|website=www.cafeaulait.org|access-date=2019-04-29}}</ref>

==== Syntax ====
<syntaxhighlight lang="java">
condition ? expression 1 : expression 2
</syntaxhighlight>condition: An expression which is evaluated as a [[Boolean algebra|boolean]] value.

expression 1, expression 2: Expressions with values of any type.

If the condition is evaluated to true, the expression 1 will be evaluated. If the condition is evaluated to false, the expression 2 will be evaluated.

It should be read as: "If condition is true, assign the value of expression 1 to result. Otherwise, assign the value of expression 2 to result."

==== Association property ====
The conditional operator is right-associative, meaning that operations are grouped from right to left. For example, an expression of the form a ? b : c ? d : e is evaluated as a ? b : (c ? d : e).<ref name=":0" /> The exception is [[PHP]], in which it was left-associative prior to version 8, and is non-associative thereafter.<ref>https://www.php.net/manual/en/language.operators.comparison.php#language.operators.comparison.ternary</ref>

==== Examples by languages ====

===== Java =====
<syntaxhighlight lang="java">
class ConditionalDemo2 {

public static void main(String[] args) {
int value1 = 1;
int value2 = 2;
int result;
boolean someCondition = true;
result = someCondition ? value1 : value2;

System.out.println(result);
}
}

</syntaxhighlight>In this example, because ''someCondition'' is true, this program prints "1" to the screen. Use the ?: operator instead of an if-then-else statement if it makes your code more readable; for example, when the expressions are compact and without side-effects (such as assignments).

===== C++ =====
<syntaxhighlight lang="c++">
#include <iostream>

int main() {
int x = 1;
int y = 2;
std::cout << ( x > y ? x : y ) << " is the greater of the two." << std::endl;
}

</syntaxhighlight>There are several rules that apply to the second and third operands in C++:

* If both operands are of the same type, the result is of that type
* If both operands are of arithmetic or enumeration types, the usual arithmetic conversions (covered in Standard Conversions) are performed to convert them to a common type
* If both operands are of pointer types or if one is a pointer type and the other is a constant expression that evaluates to 0, pointer conversions are performed to convert them to a common type
* If both operands are of reference types, reference conversions are performed to convert them to a common type
* If both operands are of type void, the common type is type void
* If both operands are of the same user-defined type, the common type is that type.<ref name=":1">{{Cite web|url=https://docs.microsoft.com/en-us/cpp/cpp/conditional-operator-q|title=Conditional Operator: ?|last=mikeblome|website=docs.microsoft.com|language=en-us|access-date=2019-04-29}}</ref>

===== C# =====
<syntaxhighlight lang="csharp">
// condition ? first_expression : second_expression;

static double sinc(double x)
{
return x != 0.0 ? Math.Sin(x) / x : 1.0;
}

</syntaxhighlight>
There are several rules that apply to the second and third operands ''x'' and ''y'' in C#:

* If x has type X and y has type Y:
* If an implicit conversion exists from X to Y but not from Y to X, Y is the type of the conditional expression.
* If an implicit conversion exists from Y to X but not from X to Y, X is the type of the conditional expression.
* Otherwise, no expression type can be determined, and a compile-time error occurs.
* If only one of x and y has a type, and both x and y are implicitly convertible to that type, that type is the type of the conditional expression.
* Otherwise, no expression type can be determined, and a compile-time error occurs.<ref name=":0" />

===== JavaScript =====
<syntaxhighlight lang="javascript">
var age = 26;
var beverage = (age >= 21) ? "Beer" : "Juice";
console.log(beverage); // "Beer"
</syntaxhighlight>
The conditional operator of JavaScript is compatible with the following browsers:

[[Google Chrome|Chrome]], [[Microsoft Edge|Edge]], [[Firefox]] (1), [[Internet Explorer]], [[Opera (web browser)|Opera]], [[Safari (web browser)|Safari]], Android webview, [[Google Chrome for Android|Chrome for Android]], [[Microsoft Edge|Edge Mobile]], [[Firefox for Android]] (4), Opera for Android, Safari on IOS, [[Samsung Internet]], [[Node.js]].<ref>{{Cite web |title=Conditional (ternary) operator - JavaScript |url=https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator |access-date=2019-04-29 |website=developer.mozilla.org |language=en-US}}</ref>

=== Special usage in conditional chain ===
The ternary operator is right-associative, which means it can be "chained" in the following way, similar to an if ... else if ... else if ... else chain.<ref name=":1" />

==== Examples by languages ====

===== JavaScript =====
<syntaxhighlight lang="javascript">
function example(…) {
return condition1 ? value1
: condition2 ? value2
: condition3 ? value3
: value4;
}

// Equivalent to:

function example(…) {
if (condition1) { return value1; }
else if (condition2) { return value2; }
else if (condition3) { return value3; }
else { return value4; }
}
</syntaxhighlight>

===== C/C++ =====
<syntaxhighlight lang="c++">
const double a =
expression1 ? a1
: expression2 ? a2
: expression3 ? a3
: /*otherwise*/ a4;

// Equivalent to:

double a;
if (expression1)
a = a1;
else if (expression2)
a = a2;
else if (expression3)
a = a3;
else /*otherwise*/
a = a4;

</syntaxhighlight>

=== Special usage in assignment expression ===
the conditional operator can yield a [[Value (computer science)#lrvalue|L-value]] in C/C++ which can be assigned another value, but the vast majority of programmers consider this extremely poor style, if only because of the technique's obscurity.<ref>{{Cite web|url=http://wiki.c2.com/?ConditionalOperator|title=Conditional Operator|website=wiki.c2.com|access-date=2019-04-29}}</ref>

==== C/C++ ====
<syntaxhighlight lang="cpp">
((foo) ? bar : baz) = frink;

// equivalent to:
if (foo)
bar = frink;
else
baz = frink;
</syntaxhighlight>

== See also ==
{{Portal|Computer programming}}
* {{Mono|[[?:]]}}, a conditional operator in computer programming
* [[Ternary operation]]
* [[Bitwise operation|Bitwise operators]]
* [[Short-circuit evaluation|Short-circuit boolean operators]]
* [[Operator (programming)]]

==References==
{{reflist}}

[[Category:Computer programming]]
[[Category:Operators (programming)]]
[[Category:Articles with example Java code]]

Conditional operator - Revision history

imported>RastaKins: /* "?:" */ ?: does not appear in most programming languages