• 设计模式之组合模式——Java语言描述


    组合模式又叫做部分整体模式,适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,用来表示部分以及整体层次

    介绍

    意图

    将对象组合成树形结构以表示“部分-整体”的层次结构。组合模式使得用户对单个对象和组合对象的使用具有一致性

    优点

    1. 高层模块调用简单
    2. 节点自由增加

    缺点

    在使用组合模式时,其叶子和树枝的声明都是实现类,而不是接口类,违反了依赖导致的原则

    实现

    创建一个Employee类,使用该类作为组合模型。

    创建Employee类,该类带有Employee对象的列表

    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 sal) {
          this.name = name;
          this.dept = dept;
          this.salary = sal;
          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+" ]");
       }   
    }
    

    使用 Employee 类来创建和打印员工的层次结构

    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 salesExecutive1 = new Employee("Richard","Sales", 10000);
          Employee salesExecutive2 = new Employee("Rob","Sales", 10000);
     
          CEO.add(headSales);
          CEO.add(headMarketing);
     
          headSales.add(salesExecutive1);
          headSales.add(salesExecutive2);
     
          headMarketing.add(clerk1);
          headMarketing.add(clerk2);
     
          //打印该组织的所有员工
          System.out.println(CEO); 
          for (Employee headEmployee : CEO.getSubordinates()) {
             System.out.println(headEmployee);
             for (Employee employee : headEmployee.getSubordinates()) {
                System.out.println(employee);
             }
          }        
       }
    }
    

    输出结果

    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 ]
    
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  • 原文地址:https://www.cnblogs.com/AmosH/p/10254200.html
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