组合模式怎样表示层次结构 部分-整体关系实现

add()

remove()

getChild()

operation()

interface Component {
    void operation();
    void add(Component component);
    void remove(Component component);
    Component getChild(int index);
}

class File implements Component {
    private String name;

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

    @Override
    public void operation() {
        System.out.println("Processing file: " + name);
    }

    @Override
    public void add(Component component) {
        throw new UnsupportedOperationException("Cannot add to a file");
    }

    @Override
    public void remove(Component component) {
        throw new UnsupportedOperationException("Cannot remove from a file");
    }

    @Override
    public Component getChild(int index) {
        throw new UnsupportedOperationException("File has no children");
    }
}

class Folder implements Component {
    private String name;
    private List<Component> children = new ArrayList<>();

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

    @Override
    public void operation() {
        System.out.println("Entering folder: " + name);
        for (Component child : children) {
            child.operation(); // 递归调用
        }
    }

    @Override
    public void add(Component component) {
        children.add(component);
    }

    @Override
    public void remove(Component component) {
        children.remove(component);
    }

    @Override
    public Component getChild(int index) {
        return children.get(index);
    }
}

public class Client {
    public static void main(String[] args) {
        Component root = new Folder("Root");
        Component docs = new Folder("Documents");
        Component pics = new Folder("Pictures");

        Component file1 = new File("resume.docx");
        Component file2 = new File("photo.jpg");

        root.add(docs);
        root.add(pics);
        docs.add(file1);
        pics.add(file2);

        root.operation(); // 递归处理所有子节点
    }
}

Entering folder: Root
Entering folder: Documents
Processing file: resume.docx
Entering folder: Pictures
Processing file: photo.jpg