The ternary operator

In languages like C and Java, there is a pattern that often occurs in programs:

// Example 1
if (age >= 18)
   price = 30;
   price = 25;

// Example 2
if (turningRight)
   angle = 90;
   angle = -90;

// Example 3
if (value.equals("1"))
   b = true;
   b = false;

The common pattern in these examples is “set a variable to some value if a condition holds, otherwise set it to another value.” We can abstract it as follows:

if ( <condition> )

<name> = <value1> ;


<name> = <value2> ;

This pattern is so often used that the designers of the C language have created a shorthand construct for this, that is also available in C++ and Java.

The conditional expression


<condition> ? <expression1> : <expression2>

(a conditional expression, followed by a question mark, followed by an expression, followed by a colon “:”, followed by another expression)


The expression on the left is evaluated first. If it evaluates to “true”, the expression in the middle is evaluated and its result is returned. Otherwise, the expression on the right is evaluated and its result is returned.

For example:

price = (age >= 18) ? 30 : 25;

angle = turningRight ? 90 : -90;

b = value.equals("1") ? true : false;

This construct abstracts over the general pattern of conditional assignment to a variable. It is even slightly more powerful, because we can nest it!

For example:

price = (age <= 6) ? 5 : ((age <= 18) ? 25 : 30);

// is equivalent to:
if (age <= 6)
   price = 5;
   if (age <= 18)
      price = 25;
      price = 30;

This construct is called the conditional expression, not to be confused with the conditional statement that uses “if”.

We name:

In other words the conditional expression combines three expressions with the conditional operator.

Ternary operator

The conditional operator is also called ternary operator because it has three positions. It is called “the” ternary operator in C and Java because it is the only operator with 3 positions in the language.

Important concepts

Further reading