组合模式(Composite Pattern)的用法

组合模式主要是为了表达“部分-整体”的层次结构，例如公司的组织架构，每个部门下又有若干个下级部门，再如菜单结构，每个菜单下可能有一个或多个子菜单。

下例以员工的层级结构说明组合模式的用法。每个员工都有姓名、部门、工资等属性，每个员工可能有0个或多个下属员工。

Employee类的代码如下：

package composite;


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


public class Employee {
  private String name;
  private String department;
  private int salary;
  private List < Employee > subordinates;
  //构造函数
  public Employee(String name, String department, int salary) {
    this.name=name;
    this.department=department;
    this.salary=salary;
    this.subordinates=new ArrayList < Employee > ();
  }
  //添加下属
  public void add(Employee employee) {
    subordinates.add(employee);
  }
  //移除下属
  public void remove(Employee employee) {
    subordinates.remove(employee);
  }
  //获取下属
  public List < Employee > getSubordinates(){
    return subordinates;
  }
  //转成字符串
  public String toString() {
    return "员工（姓名："+name+"，部门："+department+"，工资："+salary+"）";
  }
}

主函数调用方式：

package main;
import composite.*;


public class CompositePattern {
  public static void main(String[] args) {
    //创建一个员工：总裁
    Employee president = new Employee("李刚","管理层",30000);
    //创建两个员工：部门领导
    Employee directorSales = new Employee("王孟","销售部",20000);
    Employee directorRND = new Employee("严明","研发部",20000);
    //创建两个员工：销售部销售员
    Employee saler1 = new Employee("孟德贵","销售部",10000);
    Employee saler2 = new Employee("肖亮高","销售部",10000);
    //创建两个员工：研发部工程师
    Employee engineer1 = new Employee("左弓成","研发部",10000);
    Employee engineer2 = new Employee("成颜发","研发部",10000);
    //总裁添加下属
    president.add(directorSales);
    president.add(directorRND);
    //销售部部门领导添加下属
    directorSales.add(saler1);
    directorSales.add(saler2);
    //研发部部门领导添加下属
    directorRND.add(engineer1);
    directorRND.add(engineer2);
    //打印输出所有员工
    System.out.println(president);
    for(Employee directorEmployee: president.getSubordinates()) {
      System.out.println(directorEmployee);
      for(Employee employee: directorEmployee.getSubordinates()) {
        System.out.println(employee);
      }
    }
  }
}