定义：将对象组合成树形结构以表示  部分--整体的层次结构

组合模式使客户端对单个对象和组合对象保持一致的方式处理

类型：结构型

优点：

1.清楚地定义分层次的复杂对象，表示对象的全部去或部分层次

2.让客户端忽略了层次的差异，方便对整个层次结构进行控制

3.简化客户端代码

4.符合开闭原则

public abstract class CatalogComponent {    public void add(CatalogComponent catalogComponent){        throw new UnsupportedOperationException("不支持添加操作");    }    public void remove(CatalogComponent catalogComponent){        throw new UnsupportedOperationException("不支持删除操作");    }    public String getName(CatalogComponent catalogComponent){        throw new UnsupportedOperationException("不支持获取名称操作");    }    public double getPrice(CatalogComponent catalogComponent){        throw new UnsupportedOperationException("不支持获取价格操作");    }    public void print(){        throw  new UnsupportedOperationException("不支持打印操作");    }}

　　

public class Course extends CatalogComponent {    private  String name;    private  double price;    public Course(String name, double price) {        this.name = name;        this.price = price;    }    @Override    public String getName(CatalogComponent catalogComponent) {        return this.name;    }    @Override    public double getPrice(CatalogComponent catalogComponent) {        return this.price;    }    @Override    public void print() {        System.out.println("Course Name:"+name+" price:"+price);    }}

　　

public class CourseCatalog extends  CatalogComponent{    private List
     
       items=new ArrayList
      
       ();    private  String name;    private  Integer level;    public CourseCatalog(String name,Integer level) {        this.name = name;        this.level=level;    }    @Override    public void add(CatalogComponent catalogComponent) {        items.add(catalogComponent);    }    @Override    public void remove(CatalogComponent catalogComponent) {        items.remove(catalogComponent);    }    @Override    public void print() {        System.out.println(this.name);        for(CatalogComponent catalogComponent:items){            if(this.level!=null){                for(int i=0;i