设计模式学习笔记--组合模式

九、组合模式

组合模式(Composite Pattern)，又称部分整体模式，用于把一组相似的对象当作一个单一的对象。组合模式依据树形结构来组合对象，用以表示部分及整体层次。

介绍

将对象组合成树形结构以表示”部分-整体”层次结构，使用户对单一对象和组合对象的使用具有一致性。

常用于单一和组合对象树形结构的表示，或者给予用户一致性体验的场景。

比如：复杂的算术表达式，内嵌算术表达式，可以视作部分与整体的例证。

- 优点：高层代码调用简单、节点自由增加。

- 缺点：使用组合模式时，其

叶子

和

树枝

的声明都是实现类，而非接口，违反了依赖倒置原则。

实现

定义一个实体类

Employee

用作组合模型类。

CompositePatternDemo

用于演示使用

Employee

类添加部门层次结构，并输出所有员工。



- 创建实体类

Employee.java

import java.util.ArrayList;
import java.util.List;

public class Employee {
private String name;
private String dept;
private int salary;
private List<Employee> subordinates;

//构造函数
public Employee(String name,String dept,int salary){
this.name = name;
this.dept = dept;
this.salary = salary;
subordinates = new ArrayList<Employee>();
}
public void add(Employee e){
subordinates.add(e);
}
public void remove(Employee e){
subordinates.remove(e);
}
public List<Employee> getSubordinates(){
return subordinates;
}

public String toString(){
return ("Employee : [ Name : " + name + ", dept : " + dept + ",salary : "+ salary + " ]");
}
}

演示

CompositePatternDemo.java

public class CompositePatternDemo {
public static void main(String[] args){
Employee CEO = new Employee("John","CEO",30000);
Employee headSales = new Employee("Robert","Head Sales",20000);
Employee headMarketing = new Employee("Michel","Head Marketing",20000);

Employee clerk1 = new Employee("Laura","Marketing",10000);
Employee clerk2 = new Employee("Bob","Marketing",10000);

Employee salesExe1 = new Employee("Richard","Sales",10000);
Employee salesExe2 = new Employee("Rob","Sales",10000);

CEO.add(headSales);
CEO.add(headMarketing);

headSales.add(salesExe1);
headSales.add(salesExe2);

headMarketing.add(clerk1);
headMarketing.add(clerk2);

//输出该组织员工信息
System.out.println(CEO);
for(Employee headEmployee:CEO.getSubordinates()){
System.out.println(headEmployee);
for(Employee employee : headEmployee.getSubordinates()){
System.out.println(employee);
}
}
}
}

输出

Employee :[ Name : John, dept : CEO, salary :30000 ]
Employee :[ Name : Robert, dept : Head Sales, salary :20000 ]
Employee :[ Name : Richard, dept : Sales, salary :10000 ]
Employee :[ Name : Rob, dept : Sales, salary :10000 ]
Employee :[ Name : Michel, dept : Head Marketing, salary :20000 ]
Employee :[ Name : Laura, dept : Marketing, salary :10000 ]
Employee :[ Name : Bob, dept : Marketing, salary :10000 ]