CODEWITHSUNDEEP
javaconditional-operator
Varun Sharma
Varun Sharma

Reputation: 39

Ternary Operator return values

x>5 ? list1.add(something) : list2.add(something);

Why do I have to take the return value from expressions of ternary operator? I should have the option to ignore the return value.

It's forcing me to take the return value like below

boolean y = x>5 ? list1.add(something) : list2.add(something);

Upvotes: 0

Views: 925

Answers (4)

Eklavya
Eklavya

Reputation: 18430

Because the conditional operator (?:) returns one of two values depending on the value of a Boolean expression.

It does not execute because it's an expression not a statement.

Upvotes: 0

Andy Turner
Andy Turner

Reputation: 140319

The conditional ?: operator produces an expression (which means it's a bit of the syntax tree which has a value when it is executed). However, it's not a statement expression, meaning you can't just add a ; to the end of it to make a statement.

Examples of statement expressions are method invocations, constructor invocations, pre/post-increments. These make sense to stand by themselves as a statement, because they have (or can have) side effects. You can take the expression i++, add a semicolon i++;, and you have a valid, meaningful statement.

Non-statement expressions like addition 1 + 2 don't make sense by themselves. It's a bit like saying "cat and dog": it's not a "whole sentence". A conditional operator makes something like "if rain then cat else dog", which doesn't make much sense either.

If you find yourself wanting to write a conditional expression as a statement, just use an if/else statement instead.

Upvotes: 2

khelwood
khelwood

Reputation: 59104

The conditional operator is part of an expression, which means its purpose is to be evaluated. If you're not trying to get a value you shouldn't be using the conditional operator. That's what if statements are for.

Though in this case, it looks like you could achieve the effect you want using:

(x > 5 ? list1 : list2).add(something);

Upvotes: 2

Federico klez Culloca
Federico klez Culloca

Reputation: 27119

For the same reason you can't do 1 + 1; on its own: because an expression by itself is not a statement (as the actual error message tells you).

Upvotes: 3

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