Description Sean Van Gorder 2014-07-24 13:15:18 EDT

When null type annotation is used to mark a Map's value type as @NonNull, Eclipse assumes that the return type of Map.remove(Object) includes the @NonNull annotation, and therefore cannot be null. This makes it impossible to check the return value for null (indicating the map did not contain the given key) without generating bogus warnings.

Example:


@NonNullByDefault({})
public class NullTest {
    public static void main(String[] args) {
        Map<Integer, @NonNull String> map = new HashMap<>();
        String val = map.remove("badkey");
        if (val == null) { // WARNING 1
            System.out.println("NULL"); // WARNING 2
        }
    }
}


The above code will generate two bogus warnings:
WARNING 1: Null comparison always yields false: The variable val cannot be null at this location
WARNING 2: Dead code

However, running the code will print "NULL".