import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Objects;

public class ArticleRepository {
    private final List<Article> articles = new ArrayList<>();

    public void add(Article article) {
        if (article != null) {
            articles.add(article);
        }
    }

    public void addAll(Collection<Article> newArticles) {
        if (newArticles == null || newArticles.isEmpty()) {
            return;
        }
        for (Article article : newArticles) {
            add(article);
        }
    }

    public List<Article> getAll() {
        return new ArrayList<>(articles);
    }

    public void clear() {
        articles.clear();
    }

    static class Article {
        private String title;
        public Article(String title) { this.title = title; }
        public String getTitle() { return title; }
    }

    public static void main(String[] args) {
        ArticleRepository repo = new ArticleRepository();
        System.out.println("=== 测试 ArticleRepository ===");
        System.out.println("初始大小：" + repo.getAll().size());

        repo.add(new Article("文章1"));
        System.out.println("添加一个后大小：" + repo.getAll().size());

        ArrayList<Article> list = new ArrayList<>();
        list.add(new Article("文章2"));
        list.add(null);
        list.add(new Article("文章3"));
        repo.addAll(list);
        System.out.println("添加多个后大小：" + repo.getAll().size());

        repo.addAll(null);
        System.out.println("过滤null后大小：" + repo.getAll().size());
    }
}