[FIXED] what is the correct way to define Async

Issue

It seems that both are working. But should I annotate @Async in interface or implementation class?

public interface Test {

    @Async
    void A()

    void B();
}

public class TestImpl implements Test {

    @Override
    void A(){}

    @Override
    @Async
    void B(){}
}

Solution

To flesh out your example --

public interface Test{
    @Async
    void A()

    void B();
}

public class TestImpl implements Test {
    @Override
    void A(){}

    @Override
    @Async
    void B(){}
}

public class AnotherTestImpl implements Test {
    @Override
    void A(){}

    @Override
    void B(){}
}

For both TestImpl and AnotherTestImpl, the A() method is async -- that's inherited from the interface.

On the other hand, B() is not async in the interface. TestImpl declares its implementation as async, so it's async there. But AnotherTestImpl does not, so it's also not async there.

| Method | Interface | TestImpl | AnotherTestImpl |
|--------|-----------|----------|-----------------|
| A()    | async     | async    | async           |
| B()    | not async | async    | not async       |

Basically, if you declare it on the interface method, it will be inherited by all implementors.

Answered By - Roddy of the Frozen Peas
Answer Checked By - Pedro (JavaFixing Volunteer)