abstract class Component {
  protected String name;

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

  abstract public void add(Component c);
  abstract public void remove(Component c);
  abstract public void display();
}

import java.util.*;

public class Composite extends Component {
  private ArrayList children = new ArrayList();

  public Composite(String name) {
    super(name);
  }

  public void add(Component c) {
    children.add(c);
  }

  public void remove(Component c) {
    children.remove(c);
  }

  public void display() {
    System.out.println(name);
    for (int i=0;i<children.size();i++) {
      Component c = (Component)children.get(i);
      c.display();
    }
  }
}

public class Leaf extends Component {
  public Leaf(String name) {
    super(name);
  }

  public void add(Component c) {
    System.out.println("LeafにはComponentを追加できません");
  }
  public void remove(Component c) {
    System.out.println("Leafから削除できるComponentはありません");
  }
  public void display() {
    System.out.println(name);
  }
}

public class Client {
  public static void main(String[] args) {
    Composite root = new Composite("root");
    root.add(new Leaf("1"));
    root.add(new Leaf("2"));

    Composite compA = new Composite("compA");
    compA.add(new Leaf("A1"));
    compA.add(new Leaf("A2"));
    root.add(compA);

    Composite compB = new Composite("compB");
    compB.add(new Leaf("B1"));
    compB.add(new Leaf("B2"));
    compB.add(new Leaf("B3"));
    root.add(compB);

    root.display();
  }
}

C:\JavaHello\Composite>java Client
root
1
2
compA
A1
A2
compB
B1
B2
B3

C:\JavaHello\Composite>