问题
I think this question is a general programming question, but let's assume I'm asking this for Java.
what does the following statement do ?
return a ? (b || c) : (b && c);
I have seen the syntax with ?'s and :'s in many topics at SO, this particular one I found in Check if at least two out of three booleans are true
But I don't know what they mean, so how to use them, and I believe it's something very useful for me.
Thanks !
回答1:
That's the conditional operator. It means something like:
condition ? value-if-true : value-if-false;
So in your case, it returns b || c if a is true, and b && c if a is false.
回答2:
This is known as a ternary statement; it's shorthand for an if-else block - you can google that for more info.
Your example is equivalent to
if (a) {
return (b || c);
} else {
return (b && c);
}
回答3:
condition ? first statement : second statement
if condition is true then first statement is executed otherwise the second statement
回答4:
It's the ternary operator, the whole statement expands to something more like this:
if a == true then
if b == true or c == true then
return true
else
if b == true and c == true then
return true
As your link says a much more elegant way to check if at least 2 out of three booleans are true when applied in this way!
回答5:
its an conditional operator... jst like if and else....
e.g----
a<b ? 4 :5 where a= 2 and b=5
as a is less then b.... then this operator will return 4... else it return 5....
in short... if your condition i.e statement before ? is correct then it returns 1st value.. i.e statement before colon.... else it returns 2nd value......
回答6:
According to your code, return a ? (b || c) : (b && c);
Result will be like this :
if a == true , then result = b || c otherwise result = b && c
its a ternary operator & used in most of the languages C,C++, java, Javascript
来源：https://stackoverflow.com/questions/16910359/what-does-and-do-in-boolean-statements