组合模式（Composite）

// Component:public abstract class Component {

    public abstract void doSomething();    public void addChild(Component child){        throw new UnsupportedOperationException("对象不支持这个功能");
    }    public void removeChild(Component child){        throw new UnsupportedOperationException("对象不支持这个功能");
    }    public Component getChildren(int index){        throw new UnsupportedOperationException("对象不支持这个功能");
    }    public List<Component> getAll(){        throw new UnsupportedOperationException("对象不支持这个功能");
    }
}// Leaf:public class Leaf extends Component {
    private String name;    public Leaf(String name){        this.name = name;
    }    @Override
    public void doSomething() {
        System.out.println(name);
    }
}// Composite:public class Composite extends Component {
    private List<Component> list;    //遍历所有元素
    @Override
    public void doSomething() {        if(list != null && list.size()!=0){            //如果是Composite对象 会递归
            list.forEach(element -> element.doSomething());
        }else {
            System.out.println("元素为空");
        }
    }    @Override
    public void addChild(Component child) {        if(list == null){
            list = new ArrayList<>();
        }
        list.add(child);
    }    @Override
    public void removeChild(Component child) {        if(list != null){
            list.remove(child);
        }
    }    @Override
    public Component getChildren(int index) {        if(list != null){            if(index >= 0 && index < list.size()){                return list.get(index);
            }
        }        return null;
    }    @Override
    public List<Component> getAll() {        return this.list;
    }
}//Clientpublic class Client {
    public static void main(String[] args) {       //定义所有的组合对象
       Component root = new Composite("服装");
       Component c1 = new Composite("男装");
       Component c2 = new Composite("女装");       //定义所有的叶子对象
       Component leaf1 = new Leaf("衬衣");
       Component leaf2 = new Leaf("夹克");
       Component leaf3 = new Leaf("裙子");
       Component leaf4 = new Leaf("套装");       //按照树的结构来组合组合对象和叶子对象
       root.addChild(c1);
       root.addChild(c2);      
       c1.addChild(leaf1);
       c1.addChild(leaf2);     
       c2.addChild(leaf3);
       c2.addChild(leaf4);       //调用根对象的输出功能来输出整棵树
       root.doSomething();
    }
}

商品的类别树：
    +服装
        +男装
            -衬衣            -夹克        +女装
            -裙子            -套装