The ? boolean zen operator

Question

Ive never used the ? operator before and i'm trying to figure out how it works.

I have been reading countless pages and decided to try for my self.

i have the following statement:

 getSelection().equalsIgnoreCase("Måned") ? calendarView.currentlyViewing.set(Calendar.Year) : showPopup();

So as far as i cant understand if the left hand side (boolean) is true it will set my calendarView.to year and if not (getSelection is not equal to måned) it will call the method showPopup();

but when i type this into eclipse i get a syntax error.

can someone explain what i am doing wrong?

The suggested usage is this: `$name = isGirl()? 'Lauren' : 'Bob'` — andy, Mar 27 '13 at 11:39
It's difficult to tell without an error message but my guess is that both these methods have a `void` return type. That's not how `?:` works, both statements on the RHS of `?` should evaluate to a non-void value. — biziclop, Mar 27 '13 at 11:40

score 15 · Accepted Answer · answered Mar 27 '13 at 11:38

You're trying to use the conditional ? : operator to decide which statement to execute. That's not its intention. The conditional operator can't be used as a statement - it's only to choose which expression to use as the overall result.

So this is fine:

foo(condition ? nonVoidMethod1() : nonVoidMethod2());

but this isn't:

condition ? voidMethod1() : voidMethod2();

You should just use an if statement here:

if (getSelection().equalsIgnoreCase("Måned")) {
    calendarView.currentlyViewing.set(Calendar.Year);
} else {
    showPopup();
}

Thank you i understand it now :P so the left hand side is a condition and then the right hand side decides what the variable needs to be — Marc Rasmussen, Mar 27 '13 at 11:52

The ? boolean zen operator

1 Answers1