组合模式

组合多个对象形成树形结构以表示“整体-部分”的结构层次。Component ：组合中的对象接口，定义共有接口；Leaf：“部分”，叶子对象；Composite：容器，“整体”对象，实现与叶子对象有关操作。

public abstract class File {
    String name;

    public File(String name) {
        this.name = name;
    }

    public abstract void show();
}

public class ImageFile extends File {
    public ImageFile(String name) {
        super(name);
    }

    @Override
    public void show() {
        System.out.println(name);
    }
}

public class VideoFile extends File {
    public VideoFile(String name) {
        super(name);
    }

    @Override
    public void show() {
        System.out.println(name);
    }
}

public class Folder extends File {
    private List<File> files;

    public Folder(String name) {
        super(name);
        this.files = new ArrayList<>();
    }

    @Override
    public void show() {
        System.out.println(name);
        files.forEach(File::show);
    }

    public void add(File file) {
        files.add(file);
    }
}

@Test
public void CompositeTest() {
    Folder folder = new Folder("admin");
    folder.add(new ImageFile("logo"));
    folder.add(new VideoFile("MV"));
    folder.show();
}