Unnecessary @SuppressWarnings("unused")

Question

I'm getting a compiler warning for the @SuppressWarnings annotation in eclipse for the code:

@Override
public boolean doSomething(@SuppressWarnings("unused") String whatever) throws AnException {
    throw new AnException("I'm still in bed and can't do anything until I've had a shower!");
}

It looks like a yellow squiggle under the word "unused" and on mouse hover I get the tooltip Unnecessary @SuppressWarnings("unused").

I think another developer is being prompted to put in these annotations by eclipse and I'm basically being prompted to take them out. How can I configure eclipse to prompt me to put the @SuppressWarnings annotation in instead of it complaining about it?

If anyone would like to comment on best practice here then that would also be most welcome.

It really depends on if you like seeing squggily lines in your code. It drives me mad. — Jivings, Mar 02 '12 at 10:27
In case someone is coming from a web search like I did: There is a way to disable a false warning about redundant suppression in IDEA: `@SuppressWarnings({ "RedundantSuppression", "" })` — java.is.for.desktop, Feb 09 '21 at 00:58

score 69 · Accepted Answer · answered Mar 02 '12 at 10:29

In the code in your question, the @SuppressWarnings("unused") annotation is unnecessary because the method is either overriding another method from a superclass or implementing an interface. Even if you don't actually use the whatever parameter it's mandatory to declare it, otherwise the @Override annotation will produce an error (you'd be changing the signature of the overridden method if you removed the parameter.)

In some older versions of Eclipse the code as shown would not cause a warning, but in more recent releases it does. I believe it's a valid warning, and I'd rather remove the @SuppressWarnings("unused") in this case.

Furthermore, in more recent versions the "unused" warning has become more refined - if there is an annotation with runtime retention policy attached to the method, the unused warning is suppressed (as it should). — Antti Haapala -- Слава Україні, Nov 29 '14 at 13:09

score 26 · Answer 2 · answered Mar 02 '12 at 10:15

26

Go to

Window → Preferences → Java → Compiler → Errors/Warnings → Annotations.

And select Ignore for Unused '@SuppressWarnings` token.

answered Mar 02 '12 at 10:15

aioobe

413,195
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For reference: In IntelliJ it's called "Redundant suppression" – Qw3ry Oct 28 '20 at 10:17

score 6 · Answer 3 · answered Sep 04 '12 at 06:23

In my code there's no inheritance defining the 3 methods with @SuppressWarnings("unused")

This code gives 'Unnecessary @SuppressWarnings("unused")' in Eclipse Juno (latest version), but if I remove the @SuppressWarnings("unused"), I get "Constructor/Method is never used" warnings in IntelliJ IDEA 11.1.3

The methods aren't directly used in the project, only by 3rd party products Jackson, JAXB & GSON, so IntelliJ is right, I would say ...

public class EmailUnsendable extends SkjemaError {

    private NestedCommand command;        // Can't be Command (interface) because of GSON!

    @SuppressWarnings("unused")            // Used by Jackson/JAXB/GSON
    public EmailUnsendable() {
    }

    public EmailUnsendable(String referenceNumber, String stackTrace, NestedCommand command) {
        super(referenceNumber, stackTrace);
        this.command = command;
    }

    @SuppressWarnings("unused")            // Used by Jackson/JAXB/GSON
    public NestedCommand getCommand() {
        return command;
    }

    @SuppressWarnings("unused")            // Used by Jackson/JAXB/GSON
    public void setCommand(NestedCommand command) {
        this.command = command;
    }
}

I believe this is an error in Eclipse.

Doh, I tried to submit a bug on eclipse.org, but the website is just too complicated - hope that someone gives them this bug report — Torben Vesterager, Sep 04 '12 at 06:50
I would say Eclipse is right. Accessing public no-arg constructors via reflection is a frequent pattern in Java -- just like here, in fact. — Alice Purcell, Oct 12 '13 at 19:29
@SkyKelsey I switched to IntelliJ at WMdata in Århus in 2003 and have tried never to use anything else ... even when the customer asked me to ;-) — Torben Vesterager, Aug 26 '17 at 11:42

David Carboni · Answer 4 · 2012-03-05T12:59:38.730

5

Alternatively, if you think it's more correct to delete the SuppressWarnings annotation:

Window -> Preferences -> Java -> Compiler -> Errors/Warnings -> Unnecessary code -> Value of parameter is not used

and select Ignore in overriding and implementing methods

edited Mar 05 '12 at 12:59

answered Mar 05 '12 at 11:11

David Carboni

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This method is not correct in any way. IDE warnings are very important, and disabling them would be a big mistake. Seeing errors at Compile Time or Run Time is a primitive approach. – agitrubard Apr 27 '23 at 07:12

score 0 · Answer 5 · answered Apr 27 '23 at 07:09

While I agree with what you're saying, there are specific situations where there is no alternative but to use this method. As another colleague mentioned, there may be functions used indirectly within a project that do not use this method, and removing it without knowledge of its purpose could cause issues.

An example of this could be validations done using the @AssertTrue annotation. The following example shows a validation added to check the possible values for the Status field, but this method is used by Spring and not called from any other part of the project. In this scenario, I see no harm in using the @SuppressWarnings("unused") annotation.

@AssertTrue
@SuppressWarnings("unused")
private boolean isStatusValid() {

    if (this.status == null) {
        return true;
    }

    EnumSet<Status> acceptedStatuses = EnumSet.of(Status.A, Status.P);
    return EnumValidation.anyOf(status, acceptedStatuses);
}

Unnecessary @SuppressWarnings("unused")

5 Answers5