composite模式：
将对象组合成树形结构以表示“整体—部分”的层次结构。Composite模式使单个对象和组合对象的使用具有一致性。下面给出这个模式的结构图：
如果把Composite模式看成是树形结构的话，那么它主要角色有：1) 树干角色(Component)：该角色是一个抽象类，它定义了一些操作增删树叶（Leaf）的操作。2) 树枝角色(Composite)：树枝上有很多树干，树枝也是树干的一种。3) 树叶角色(Leaf):树干上的树叶，也就是Component中的具体操作对象。示例代码：public abstract class MovieClass { public String name; public ArrayList<MovieClass> list; public abstract void add(MovieClass component); public abstract void remove(MovieClass component); public abstract void display(); } public class Program extends MovieClass { public Program(String name) { this.name = name; } public void add(MovieClass component) { System.out.println("you can't add component to a proagram object"); } public void display() { System.out.println("----------" + name); } public void remove(MovieClass component) { System.out.println("you can't remove component to a proagram object"); } } import java.util.ArrayList; public class ConcreteMovieClass extends MovieClass { public ConcreteMovieClass(String name) { this.name = name; list = new ArrayList<MovieClass>(); } public void add(MovieClass component) { list.add(component); } public void remove(MovieClass component) { if (list.contains(component)) { list.remove(component); } } public void display() { System.out.println(name); for (MovieClass mc : list) { mc.display(); } } } public static void main(String args[]) { Program pro = new Program("大汉天子"); Program pro2 = new Program("贞观长歌"); ConcreteMovieClass cmc = new ConcreteMovieClass("电视连续剧");// 一级分类 cmc.add(pro); cmc.add(pro2); Program pro3 = new Program("满城尽带黄金甲"); Program pro4 = new Program("色戒"); ConcreteMovieClass cmc2 = new ConcreteMovieClass("最新影视");// 一级分类 cmc2.add(pro3); cmc2.add(pro4); Program pro5 = new Program("越狱"); Program pro6 = new Program("英雄"); ConcreteMovieClass secondCmc = new ConcreteMovieClass("热播美剧");// 二级分类 secondCmc.add(pro5); secondCmc.add(pro6); cmc2.add(secondCmc);// 在一级分类（最新影视)下添加二级分类热播美剧 ConcreteMovieClass root = new ConcreteMovieClass("root"); root.add(cmc); root.add(cmc2); //root.add(secondCmc); root.display();// 显示节目列表 } }
输出结果：root电视连续剧----------大汉天子----------贞观长歌最新影视----------满城尽带黄金甲----------色戒热播美剧----------越狱----------英雄
