设计模式 合成模式

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  设计模式 - 合成模式

  合成模式用于需要以类似方式将一组对象视为单个对象的情况。合成模式根据树结构组成对象，以表示部分以及整个层次结构。这种设计模式属于结构模式，因为该模式创建了一组对象的树形结构。

  此模式创建一个包含其自己的对象组的类。此类提供了修改其相同对象组的方法。

  我们通过以下示例演示合成模式的使用，在该示例中我们将显示组织的员工层次结构。
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  实例

  我们有一个Employee类，它充当合成模式参与者类。CompositePatternDemo，我们的演示类将使用Employee类添加部门级别的层次结构并打印所有员工。

  

  第1步 - 创建员工具有列表类员工的对象。 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;
  
     // constructor
     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+" ]");
     }   
  }
  

  第2步 - 使用Employee类创建和打印员工层次结构。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 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);
  
        //print all employees of the organization
        System.out.println(CEO); 
        
        for (Employee headEmployee : CEO.getSubordinates()) {
           System.out.println(headEmployee);
           
           for (Employee employee : headEmployee.getSubordinates()) {
              System.out.println(employee);
           }
        }         
     }
  }
  

  第3步 - 验证输出。

  
  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 ]