Java结构型模式中的组合模式详解

//抽象节点
public abstract class Component {
    abstract void add(Component component);
    abstract void remove(Component component);
    abstract Component getChild(int i);
    abstract void operation();
}
//叶子节点
class Leaf extends Component{
    private String name;
    public Leaf(String name) {
        this.name = name;
    }
    @Override
    void add(Component component) {}
    @Override
    void remove(Component component) {}
    @Override
    Component getChild(int i) {
        return null;
    }
    @Override
    void operation() {
        System.out.print(name);
    }
}
//树枝节点
class Composite extends Component{
    private ArrayList<Component> children = new ArrayList<>();
    @Override
    void add(Component component) {
       children.add(component);
    }
    @Override
    void remove(Component component) {
        children.remove(component);
    }
    @Override
    Component getChild(int i) {
        return children.get(i);
    }
    @Override
    void operation() {
        children.forEach(Component::operation);
    }
}

public class Client {
    public static void main(String[] args) {
        Component level1 = new Composite();
        level1.add(new Leaf("1"));
        level1.add(new Leaf("2"));
        Component level2 = new Composite();
        level2.add(new Leaf("2.1"));
        level1.add(level2);
        level1.operation();
    }
}