What’s the annotation that can help in this case, ...

# announcements

[Gopal S Akshintala]

What’s the annotation that can help in this case, for Java interoperability? org.jetbrains.annotations.NotNull doesn’t work on Generic param types 😞

fun someFun(list: List<@NotNull String>)

[Alexey Belkov [JB]]

It should work. Try to use some more recent annotations package like "org.jetbrainsannotations20.0.0"

[Gopal S Akshintala]

@Alexey Belkov [JB] Thanks you are right… I was experimenting on a unit test and I forgot to add this entry testCompileOnly("org.jetbrains:annotations:20.1.0")
It now works without an exception, but I see no warning or runtimeexception when I did this. Aren’t these annotations supposed to help IDE at compile time?

@Test
  void notNull() {
      //someFun(null);
      var list = new ArrayList<String>();
      list.add("");
      list.add(null);
      NotNullKt.someFun(list);
  }

[Gopal S Akshintala]

fun someFun(list: List<@NotNull String>) {
    list.map { println(it) }
}

[Gopal S Akshintala]

I hv this option as well

[Gopal S Akshintala]

If it’s only for compile time, is there any significance to use it for java interoperability when Kotlin already has a way to express nullability?

[Alexey Belkov [JB]]

You're right, it's pointless to annotate anything in Kotlin code. These annotations are intended for Java code. For example, you can do this:

import org.jetbrains.annotations.NotNull;
import java.util.ArrayList;

public class J {
public static void main(String[] args) {
ArrayList<@NotNull String> list = new ArrayList<@NotNull String>();
list.add(null); // Passing 'null' argument to parameter annotated as @NotNull
}
}

[Gopal S Akshintala]

Thanks @Alexey Belkov [JB]!