模式意图
使对象组合成树形的结构。使用户对单个对象和组合对象的使用具有一致性。
应用场景
1 表示对象的 部分-整体 层次结构
2 忽略组合对象与单个对象的不同，统一的使用组合结构中的所有对象。
模式结构
【安全的组合模式】
这种组合模式，叶子节点，也就是单个对象不具有对象的控制功能。仅仅有简单的业务操作。
1 package com.xingoo.composite.safe; 2 3 import java.util.ArrayList; 4 import java.util.List; 5 6 interface Component{ 7 Composite getCmposite(); 8 void sampleComposite(); 9 }10 11 class Leaf implements Component{12 13 public Composite getCmposite() {14 return null;15 }16 17 public void sampleComposite() {18 System.out.println("Leaf operation");19 }20 21 }22 23 class Composite implements Component{24 25 private List list = new ArrayList();26 27 public void add(Component component){28 list.add(component);29 }30 31 public void remove(Component component){32 list.remove(component);33 }34 35 public Composite getCmposite() {36 return this;37 }38 39 public void sampleComposite() {40 System.out.println("Composite operation");41 for(Component com : list){42 com.sampleComposite();43 }44 }45 46 }47 public class Client {48 public static void main(String[] args) {49 Component leaf1 = new Leaf();50 Component leaf2 = new Leaf();51 Component composite = new Composite();52 composite.getCmposite().add(leaf1);53 composite.getCmposite().add(leaf2);54 composite.getCmposite().sampleComposite();55 }56 } 执行结果
Composite operationLeaf operationLeaf operation
【透明的组合模式】
这种组合模式，叶子节点与组合对象具有相同的方法，外表看来毫无差异。不过叶子节点的处理方法默认为空。忽略叶子节点，与组合对象的差异性。
1 package com.xingoo.composite.transparent; 2 3 import java.util.ArrayList; 4 import java.util.List; 5 6 interface Component{ 7 public void SampleOperation(); 8 public void add(Component component); 9 public void remove(Component component);10 public Component getComponent();11 }12 13 class Leaf implements Component{14 public void SampleOperation() {15 System.out.println("leaf operation!");16 }17 18 public void add(Component component) {19 20 }21 22 public void remove(Component component) {23 24 }25 26 public Component getComponent(){27 return this;28 }29 }30 31 class Composite implements Component{32 33 private List list = new ArrayList();34 35 public void SampleOperation() {36 System.out.println("composite operation!");37 for(Component com : list){38 com.getComponent().SampleOperation();39 }40 }41 42 public void add(Component component) {43 list.add(component);44 }45 46 public void remove(Component component) {47 list.remove(component);48 }49 50 public Component getComponent(){51 return this;52 }53 }54 public class Client {55 public static void main(String[] args) {56 Component leaf1 = new Leaf();57 Component leaf2 = new Leaf();58 Component leaf3 = new Leaf();59 Component composite1 = new Composite();60 Component composite = new Composite();61 62 composite1.add(leaf3);63 64 composite.getComponent().add(leaf1);65 composite.getComponent().add(leaf2);66 composite.getComponent().add(composite1);67 68 composite.getComponent().SampleOperation();69 }70 } 本例中的结构层次
执行结果
composite operation!leaf operation!leaf operation!composite operation!leaf operation!