GenericsAdd (capture ) in Set cannot be applied to (ConstraintViolation)

Question

I have the following code:

UniqueConstraintViolation violation = new UniqueConstraintViolationImpl();
Set<? extends javax.validation.ConstraintViolation> violations = new HashSet<UniqueConstraintViolation>();
violations.add(violation);
throw new javax.validation.ConstraintViolationException(violations);

where UniqueConstraintViolation is interface extended javax.validation.ConstraintViolation and UniqueConstraintViolationImpl is class implemented UniqueConstraintViolation

While compiling I get following error

java:42: error: no suitable method found for add(UniqueConstraintViolation) violations.add(violation); ^ method Collection.add(CAP#1) is not applicable (argument mismatch; UniqueConstraintViolation cannot be converted to CAP#1 ) method Set.add(CAP#1) is not applicable (argument mismatch; UniqueConstraintViolation cannot be converted to CAP#1 ) where CAP#1 is a fresh type-variable: CAP#1 extends ConstraintViolation from capture of ? extends ConstraintViolation C:\workspace\zcts-travel\crud-rest\src\main\java\ru\zcts\crud\AbstractResource.java:43: error: incompatible types: Set cannot be converted to Set> throw new javax.validation.ConstraintViolationException(violations);
                                                                ^   where CAP#1 is a fresh type-variable:
CAP#1 extends ConstraintViolation from capture of ? extends ConstraintViolation

I just want to pass in javax.validation.ConstraintViolationException constructor the Set with my own implementation of javax.validation.ConstraintViolation. How I can do it?

score 1 · Answer 1 · edited May 23 '17 at 12:23

1

Set<? extends javax.validation.ConstraintViolation> violations = new HashSet<UniqueConstraintViolation>();
violations.add(violation);

you can't add anything other than null to voilations because it uses ? extends javax.validation.ConstraintViolation.

read here : Java Generic with ArrayList <? extends A> add element

edited May 23 '17 at 12:23

Community

1
1

answered Nov 12 '15 at 09:39

Ramanlfc

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to solve the problem, change ``Set extends ConstraintViolation> violations = ...;`` to ``Set violations = new HashSet<>();`` – Binkan Salaryman Nov 12 '15 at 09:51
1

then `violations` won't be able to refer to `new HashSet();` – Ramanlfc Nov 12 '15 at 09:53
let type inference do it's work: ``new HashSet<>();`` thanks for the note. – Binkan Salaryman Nov 12 '15 at 09:55

Zilvinas · Accepted Answer · 2015-11-12T09:59:30.397

1

So having your constraints:

interface UniqueConstraintViolation extends ConstraintViolation<YourClass> {

}

public class UniqueConstraintViolationImpl implements UniqueConstraintViolation {
    /* your impl here */
}

This will compile:

UniqueConstraintViolation violation = new UniqueConstraintViolationImpl();

Set<UniqueConstraintViolation> violations = new HashSet<UniqueConstraintViolation>();
violations.add(violation);
throw new ConstraintViolationException(violations);

edited Nov 12 '15 at 09:59

answered Nov 12 '15 at 09:48

Zilvinas

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that hurts my eyes, even dropping the constraints would be better than wildcasting everything – Binkan Salaryman Nov 12 '15 at 09:50
@ETartaren the problem was in the `Set` declaration – Zilvinas Nov 12 '15 at 10:00

GenericsAdd (capture ) in Set cannot be applied to (ConstraintViolation)

2 Answers2