Why is the sort method not working on this custom AbstractList implementation?

Question

Android Studio is giving me a "Usage of API documented as @since 1.8+" error on the sort() line, inside the addAll() method. I'm not quite sure what this means...

All I want to do is a custom List where I can sort the List by the publishedAt property of Articles_Map.

AbstractArticlesList:

public class AbstractArticlesList extends AbstractList<Articles_Map> {
    private final List<Articles_Map> l;

    public AbstractArticlesList() {
        l = new ArrayList<>();
    }

    public Articles_Map get(int index) {
        return l.get(index);
    }

    public Articles_Map set(int index, Articles_Map element) {
        Articles_Map oldValue = l.get(index);
        l.add(index, element);
        return oldValue;
    }

    public int size() {
        return l.size();
    }

    private void doAdd(Articles_Map another) {
        l.add(another);
    }

    public void addAll(List<Articles_Map> others) {
        for (Articles_Map a : others) {
            doAdd(a);
        }
        l.sort(byPublishedAtComparator);
    }

    private final Comparator<Articles_Map> byPublishedAtComparator =
            new Comparator<Articles_Map>() {
                @Override
                public int compare(Articles_Map o1, Articles_Map o2) {
                    if (o1.publishedAt == null) {
                        return (o2.publishedAt == null) ? 0 : -1;
                    } else if (o2.publishedAt == null) {
                        return 1;
                    }
                    return o1.publishedAt.compareTo(o2.publishedAt);
                }
            };
}

Articles_Map:

public class Articles_Map {
    public final String title;
    public final String description;
    public final String url;
    public final String urlToImage;
    public final Date publishedAt;

    public Articles_Map(String title, String description, String url, String urlToImage, Date publishedAt) {
        this.title = title;
        this.description = description;
        this.url = url;
        this.urlToImage = urlToImage;
        this.publishedAt = publishedAt;
    }
}

Answer 1

sort() is new to API Level 24 (Android 7.0), courtesy of Android starting to adopt bits of Java 1.8.

Use Collections.sort() if your minSdkVersion is lower than 24.