组合模式

//抽象构件
public abstract class Component{
    public void doSomething(){
        //
    }
}
//树枝构件
public class Composite extends Component{
    private ArrayList<Component> componentArrayList=new ArrayList<Component>();
    public void add(Component component){
        this.componentArrayList.add(component);
    }
    public void remove(Component component){
        this.componentArrayList.remove(component);
    }
    public ArrayList<Component> getChildren(){
        return this.componentArrayList;
    }
}

//树叶构件
public class Leaf extends Component{
    /*
     *可以覆盖父类方法
    public void doSomething(){
    
    }
    */
}

//场景类
public class Client{
    public static void main(String[] args){
        //创建一个根节点
        Composite root=new Composite();
        root.doSomething();
        //构建一个树形节点
        Composite branch=new Composite();
        Leaf leaf=new Leaf();
        //建立整体
        root.add(branch);
        branch.add(leaf);
    }
    
    //通过递归遍历树
    public static void display(Composite root){
        for(Component c:root.getChildren()){
            if(c instanceof Leaf){//叶子节点
                c.doSomething();
            }else{//树枝节点
                display((Composite)c);
            }
        }
    }
}