Java ternary operator does not compile as a statement

Question

I run a simple example of ternary operator. I wonder why in the second case it doesn't work.

class Gun 
{
    public int hit;
}

public class Test1 {
    public static void main(String[] args) {
        Gun weapon1=new Gun();
        weapon1.hit=54;
        String es1=new String("You killed him!. Grac!");
        String es2=new String("Ops, you were noticed.");

        System.out.println((weapon1.hit>50 ? es1 : es2)); //this works fine

        weapon1.hit>50 ? System.out.println(es1) : System.out.println(es2); // this doesn't

    }
}

After all, the ternary operator is supposed to work similar to if-else statements and this if-else code works just fine:

if (weapon1.hit>50)
    System.out.println(es1);
else
    System.out.println(es2);

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - not a statement at Test1.main(Test1.java:39) That's the error I get if I uncomment the weapon1.hit>50 ? System.out.println(es1) : System.out.println(es2); line.

`System.out.println(weapon1.hit > 50 ? es1 : es2);`. Also, please learn how to format your code (just use an IDE; it does it for you) to preserve our sanity. — bcsb1001, Jun 18 '16 at 22:07
By *"doesn't work"* you mean that it **doesn't compile**? Like the string literal that is split over 3 lines won't compile? Because, you know, *"doesn't work"* is a lousy description of a problem, and if you get an error, you should show us the error, so we know for sure what you are talking about. — Andreas, Jun 18 '16 at 22:10
@Pshemo So you decided to silently fix one of at least 3 compile errors in that code? — Andreas, Jun 18 '16 at 22:19
`Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - not a statement at Test1.main(Test1.java:39)` That's the error I get if I uncomment the `weapon1.hit>50 ? System.out.println(es1) : System.out.println(es2);` line. — parsecer, Jun 18 '16 at 22:20
@Andreas I tried to limit problems to line with conditional operator (I assumed that printing multi-line string was not related to described problem since OP claims that if-else code works fine). OP still needs to improve his question farther and provide proper error description. — Pshemo, Jun 18 '16 at 22:21
@parsecer You get that error because ternary operator is an *expression*, not a *statement*. — Andreas, Jun 18 '16 at 22:23
@Tunaki Since find of the dup. Man, I couldn't even fathom that this is such a common problem that you can even *find* a dup chain on here. *Sheesh...* Lack of imagination on my part, I guess. — Andreas, Jun 18 '16 at 22:26

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

The conditional is not simply equivalent to an if-else statement.

From the specification for the Conditional Operator ?:

The conditional operator has three operand expressions. ? appears between the first and second expressions, and : appears between the second and third expressions.

The first expression must be of type boolean or Boolean, or a compile-time error occurs.

It is a compile-time error for either the second or the third operand expression to be an invocation of a void method.

edited Jun 20 '20 at 09:12

Community

1
1

answered Jun 18 '16 at 22:03

Jean Logeart

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You will not even get around to that compile-time error until you fix at least two other errors in that code. – Andreas Jun 18 '16 at 22:15

score 1 · Answer 2 · answered Jun 18 '16 at 22:03

1

Ternary operator in Java requires expression while System.out.println is a statement.

ConditionalExpression:
    ConditionalOrExpression
    ConditionalOrExpression ? Expression : ConditionalExpression

You can find docs here.

answered Jun 18 '16 at 22:03

SerCe

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You will not even get around to that problem until you fix at least two other errors in that code. – Andreas Jun 18 '16 at 22:16
Which are? The rest compiles just fine. – parsecer Jun 18 '16 at 22:32

Java ternary operator does not compile as a statement

2 Answers2