i.java

public interface I1<K, V> {
    V key(K k);
}

public interface I2<K, V> {
    V key(K k);
}

public class C implements I1<String, String>, I2<Long, Long> {
    @Override
    public String key(String s) {
        return null;
    }

    @Override
    public String key(Long aLong) {
        return null;
    }
}

iAnnotation.java

public interface I1<@Foo K, V> {
    V key(K k);
}

public interface I2<@Bar K, V> {
    V key(K k);
}

public class C implements I1<String, String>, I2<String, String> {
    @Override
    public String key(String s) {
        return null;
    }

    @Override
    public String key(Long aLong) {
        return null;
    }
}