If without else ternary operator

问题

So far from I have been searching through the net, the statement always have if and else condition such as a ? b : c. I would like to know whether the if ternary statement can be used without else. Assuming i have the following code, i wish to close the PreparedStatement if it is not null

(I am using Java programming language.)

PreparedStatement pstmt;

//.... 

(pstmt!=null) ? pstmt.close : <do nothing>;

回答1:

No, you cannot do that. Instead try this:

if(bool1 && bool2) voidFunc1();

回答2:

Why using ternary operator when you have only one choice?

if (pstmt != null) pstmt.close();

is enough!

回答3:

Just write it out?

if(pstmt != null) pstmt.close();

It's the exact same length.

回答4:

Ternary if operator is the particular ternary operator. One of a kind.

From Wiki:

In mathematics, a ternary operation is an n-ary operation with n = 3.

It means all 3 operands are required for you.

回答5:

As mentioned in the other answers, you can't use a ternary operator to do this.

However, if the need strikes you, you can use Java 8 Optional and lambdas to put this kind of logic into a single statement:

Optional.of(pstmt).ifPresent((p) -> p.close())

回答6:

A ternary operation is called ternary beacause it takes 3 arguments, if it takes 2 it is a binary operation.

And as noted above, it is an expression returning a value.

If you omit the else you would have an undefined situation where the expression would not return a value.

So as also noted in other answer, you should use an if statement.

回答7:

You cannot use ternary without else, but to do a "if-without-else" in one line, you can use Java 8 Optional class.

PreparedStatement pstmt;

//.... 

Optional.ofNullable(pstmt).ifPresent(pstmt::close); // <- but IOException will still happen here. Handle it.

回答8:

Well in JavaScript you can simply do:

expression ? doAction() : undefined

since that's what's literally actually happening in a real if statement, the else clause is simply undefined. I image you can do pretty much the same thing in (almost?) any programming language, for the else clause just put a null-type variable that doesn't return a value, it shouldn't cause any compile errors.

回答9:

Yes you can do that actually (in JavaScript at least):

condition && x = true;

or (in JavaScript, and there might be a similar way to do this in Java):

void(condition && x = true)

来源：https://stackoverflow.com/questions/20053257/if-without-else-ternary-operator

标签

java

if-statement

ternary-operator