Why is my use of the ?: conditional operator incorrect?

Question

I get a compilation error while trying to compile, \"not a statement\", and the code is:

(checkDatabaseExist())?connectToDB() : buildDB();

when

Answer 1

Adding to what @Jon Skeet said, a Ternary operator (What you're using) is designed to be used in this sort of way:

String s = someBoolean ? "someBoolean is true" : "someBoolean is false";

(condition) ? (value if true) : (value if false)

Answer 2

As stated in JLS - Section 15.25 - Conditional Operator: -

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

So, you must use an if-else construct to invoke your methods on different condition.

if (checkDatabaseExist()) {
    connectToDB();
} else {
    buildDB();
}

Answer 3

The ternary operator can not be used with methods/operations returning void.

The methods/expressions must return a value compatible with the reference type.

Answer 4

Yes, you can't use the conditional operator like that. It's intended to compute one expression or another as a result. It's not intended to be a way of choosing one statement to execute or another.

Just use:

if (checkDatabaseExist()) {
    connectToDB();
} else {
    buildDB();
}