Missing return value on Void method?

Question

The following code gives me compile-time errors: missing return value and missing return statement, what value would I return for this Void Type?

final SwingWorker<Void, Void> worker = new SwingWorker<Void, Void>() {
    @Override
    protected Void doInBackground() throws Exception {
        // some code
        if (something) {
            return;
        }
    }
}

Use return null. See http://stackoverflow.com/questions/643906/uses-for-the-java-void-reference-type — jontro, Dec 06 '12 at 18:00
@HericDenis: Then you should understand that you *do* need to return something (probably a null reference)... it's not just a normal void method with no return value. — Jon Skeet, Dec 06 '12 at 18:01
I will return null, but I was like: maybe some nullPointerException will happen idk, this is crazy — HericDenis, Dec 06 '12 at 18:02

score 32 · Accepted Answer · edited Dec 14 '20 at 15:43

32

Void is not void, change it to void type if you don't want to return anything.

Void is a class, void is type.

/**
 * The {@code Void} class is an uninstantiable placeholder class to hold a
 * reference to the {@code Class} object representing the Java keyword
 * void.
 *
 * @author  unascribed
 * @since   JDK1.1
 */

If you want Void, then you need to add return statement at end.

Example:

protected Void doInBackground() throws Exception {
    // some code
    if (something) {
       return null;
    }
    return null;
}

edited Dec 14 '20 at 15:43

Willi Mentzel

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answered Dec 06 '12 at 17:57

kosa

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Thanks, that's what I thought but I was not sure it was going to give some NullPointerException or something. Thanks – HericDenis Dec 06 '12 at 18:04
@HericDenis: I don't think it fails. See this discussion http://stackoverflow.com/questions/4261666/how-do-i-wait-for-a-swingworkers-doinbackground-method – kosa Dec 06 '12 at 18:06
there is a null missing after the first return statement – HericDenis Dec 06 '12 at 18:06
Yeah, it seems like :) Thanks @Nambari – HericDenis Dec 06 '12 at 18:09

score 1 · Answer 2 · edited Dec 14 '20 at 15:46

1

Check this. It asks to return Void with captital "V" not with simple void

final SwingWorker<Void, Void> worker = new SwingWorker<Void, Void>() {
    @Override
    protected Void doInBackground() throws Exception {
        // my code here
        return null;
    }
}

edited Dec 14 '20 at 15:46

Willi Mentzel

27,862
20
113
121

answered Dec 06 '12 at 18:02

someone

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Missing return value on Void method?

2 Answers2