import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class ArticleRepository {
    private final List<Article2> articles = new ArrayList<>();

    public void add(Article2 article) {
        if (article == null) throw new IllegalArgumentException("文章不能为空");
        articles.add(article);
    }

    public void addAll(List<Article2> newArticles) {
        if (newArticles == null) throw new IllegalArgumentException("列表不能为空");
        for (Article2 a : newArticles) {
            if (a == null) throw new IllegalArgumentException("列表中不能有空对象");
            articles.add(a);
        }
    }

    public List<Article2> getAll() {
        return Collections.unmodifiableList(articles);
    }

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

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