组合模式

将对象组合成树状层出结构，使用户能一致地使用叶子节点和分支节点

package com.jerry.design.composite; import java.util.ArrayList; import java.util.List; // 测试类 public class Test { public static void main(String[] args) { Component root = new Composite(); Component c1 = new Composite(); Component c2 = new Composite(); Component l1 = new Leaf(); Component l2 = new Leaf(); Component l3 = new Leaf(); root.addChild(c1); root.addChild(c2); root.addChild(l1); c1.addChild(l2); c1.addChild(l3); System.out.println(root.getChild(0)); System.out.println(root.getChild(1)); System.out.println(root.getChild(2)); } } interface Component{ public void doSomething(); public void addChild(Component c); public void removeChild(Component c); public Component getChild(int index); } class Composite implements Component{ private List<Component> children = null; @Override public void doSomething() { if(children!=null){ for(Component c:children){ c.doSomething(); } } } @Override public void addChild(Component c) { if(children==null){ children = new ArrayList<Component>(); } children.add(c); } @Override public void removeChild(Component c) { if(children!=null){ children.remove(c); } } @Override public Component getChild(int index) { if(children!=null){ return children.get(index); } return null; } } class Leaf extends Composite{ public void doSomething() { System.out.println("Leaf is doSomething()"); } }