What is the Java ?: operator called and what does it do?

Question

I have been working with Java a couple of years, but up until recently I haven\'t run across this construct:

int count = isHere ? getHereCount(index) : getAw         


        

Answer 1

This construct is called Ternary Operator in Computer Science and Programing techniques.
And Wikipedia suggest the following explanation:

In computer science, a ternary operator (sometimes incorrectly called a tertiary operator) is an operator that takes three arguments. The arguments and result can be of different types. Many programming languages that use C-like syntax feature a ternary operator, ?: , which defines a conditional expression.

Not only in Java, this syntax is available within PHP, Objective-C too.

In the following link it gives the following explanation, which is quiet good to understand it:

A ternary operator is some operation operating on 3 inputs. It's a shortcut for an if-else statement, and is also known as a conditional operator.

In Perl/PHP it works as:
boolean_condition ? true_value : false_value

In C/C++ it works as:
logical expression ? action for true : action for false

This might be readable for some logical conditions which are not too complex otherwise it is better to use If-Else block with intended combination of conditional logic.

We can simplify the If-Else blocks with this Ternary operator for one code statement line.
For Example:

if ( car.isStarted() ) {
     car.goForward();
} else {
     car.startTheEngine();
}

Might be equal to the following:

( car.isStarted() ) ? car.goForward() : car.startTheEngine();

So if we refer to your statement:

int count = isHere ? getHereCount(index) : getAwayCount(index);

It is actually the 100% equivalent of the following If-Else block:

int count;
if (isHere) {
    count = getHereCount(index);
} else {
    count = getAwayCount(index);
}

That's it!
Hope this was helpful to somebody!
Cheers!