Proleps

  public class Article {
      private final String title;
      private final String author;
      private final List<String> tags;

      private Article(String title, String author, List<String> tags) {
          this.title = title;
          this.author = author;
          this.tags = tags;
      }

      public String getTitle() {
          return title;
      }

      public String getAuthor() {
          return author;
      }

      public List<String> getTags() {
          return tags;
      }
  }

  public class MutableArticle extends Article {
      private String title;
      private String author;
      private List<String> tags;

      public MutableArticle() {
          super(null, null, null);
      }

      public String getTitle() {
          return title;
      }

      public void setTitle(String title) {
          this.title = title;
      }

      public String getAuthor() {
          return author;
      }

      public void setAuthor(String author) {
          this.author = author;
      }

      public List<String> getTags() {
          return tags;
      }

      public void setTags(List<String> tags) {
          this.tags = tags;
      }

  }

  public final class Article{
    public final String title;
    public final String author;
    public final List<String> tags;
    public Article(String title, String author, List<String> tags) {
      this.title = title;
      this.author = author;
      this.tags = tags;
    }
  }