Why does this basic Java boolean expression not work?

Question

Why does this not compute in Java (v1.8). Seems perfectly logical to me....

boolean banana = true;
(banana == true || false) ? System.out.println("True") : System.out.println("False");

Output message: Error: java: not a statement

Answer 1

The ternary conditional operator must return a value. The second and third operands can't be statements that don't return anything. They must be expressions that return a value.

You could switch it to :

System.out.println(banana ? "True" : "False");

Note that banana == true || false is equivalent to banana == true, which is equivalent to banana as banana itself is a boolean type.

Answer 2

How about this?

System.out.println(banana ? "true" : "false");

The ternary operator always has to return a value which we're printing.

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The other way is only using if-else statement, but it's not pretty.

if(banana)
    System.out.println("true");
else
    System.out.println("false");

Answer 3

The Java Language Specification §15.25 says:

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

Better try like this:

System.out.println(banana ? "true" : "false");

Answer 4

What you want is

boolean banana = true;
System.out.println(banana ? "True" : "False");

A ? : operator has to return a value and println is a void method. Not only does it do what you want, it is more concise.

Note

banana == true

is the same as

banana

and

x || false

is the same as

x

Also unless you need to print "True" instead of "true" you can do

System.out.println(banana);

Answer 5

You are using it incorrectly.

One use of the Java ternary operator (also called the conditional operator) is to assign the minimum (or maximum) value of two variables to a third variable, essentially replacing a Math.min(a,b) or Math.max(a,b) method call. Here's an example that assigns the minimum of two variables, a and b, to a third variable named minVal is:

minVal = (a < b) ? a : b;

You can do it like this.

if(boolean)
   System.out.println("True");
else  
   System.out.println("False");

Answer 6

I guess because Java won't allow statement like that.

Try using if statement.

boolean banana = true;
if (banana == true || false) System.out.println("True"); else System.out.println("False");

Answer 7

Because there are only false bananas: https://en.wikipedia.org/wiki/False_banana. There is not any one "true" banana. You are likely thinking of the "true plantain", see https://en.wikipedia.org/wiki/True_plantains. Changing your banana to false will allow your code to once again be copacetic with biology.