复合设计模式

复合模式说, 只是“允许客户端以通用方式对可能表示对象层次结构的对象进行操作”。

复合设计模式的优势

• 它定义了包含原始对象和复杂对象的类层次结构。
• 它使你更容易添加新的组件。
• 它通过可管理的类或接口提供结构的灵活性。

复合图案的用法

它用于：

• 当你要表示对象的全部或部分层次结构时。
• 需要将职责动态添加到单个对象时, 而不影响其他对象。对象的责任可能会不时变化。

用于复合模式的UML

复合模式中使用的元素：

让我们看看复合模式的4个元素。

1）组成部分

• 声明组成对象的接口。
• 根据需要为所有类通用的接口实现默认行为。
• 声明用于访问和管理其子组件的接口。

2）叶

• 表示组成中的叶对象。叶子没有孩子。
• 定义合成中原始对象的行为。

3）复合

• 定义具有子级的组件的行为。
• 存储子组件。
• 在组件界面中实现与子级相关的操作。

4）客户

• 通过组件接口操作合成中的对象。

注意：以上通用UML的工作流程如下。

客户端使用组件类接口与组合结构中的对象进行交互。如果收件人是叶子, 则将直接处理请求。如果接收者是复合用户, 则通常会将请求转发给其子代以执行其他操作。

复合图案示例

我们可以通过下面给出的UML图轻松理解复合设计模式的示例：

以上UML的实现：

步骤1

创建一个将被视为组件的Employee接口。

// this is the Employee interface i.e. Component.
public interface Employee {
	public  int getId();
	public String getName();
	public double getSalary();
       public void print();
	public void add(Employee employee);
       public void remove(Employee employee);
       public Employee getChild(int i);
}// End of the Employee interface.

第2步

创建一个将被视为Composite的BankManager类, 并实现Employee接口。

// this is the BankManager class i.e. Composite.
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class BankManager implements Employee {
	 private int id;
	 private String name;
	 private double salary;

	 public BankManager(int id, String name, double salary) {
	  this.id=id;	 
	  this.name = name;
	  this.salary = salary;
	 }
         List<Employee> employees = new ArrayList<Employee>();
	 @Override
	 public void add(Employee employee) {
	    employees.add(employee);
	 }
        @Override
	 public Employee getChild(int i) {
	  return employees.get(i);
	 }
	 @Override
	 public void remove(Employee employee) {
	  employees.remove(employee);
	 }	
	 @Override
	 public int getId()  {
	  return id;
	 }
	 @Override
	 public String getName() {
	  return name;
	 }
    @Override
	 public double getSalary() {
	  return salary;
	 }
	 @Override
	 public void print() {
	  System.out.println("==========================");
	  System.out.println("Id ="+getId());
	  System.out.println("Name ="+getName());
	  System.out.println("Salary ="+getSalary());
	  System.out.println("==========================");
	  
	  Iterator<Employee> it = employees.iterator();
	  
	      while(it.hasNext())  {
	        Employee employee = it.next();
	        employee.print();
	     }
	 }
}// End of the BankManager class.

第三步

创建一个Cashier类, 该类将被视为叶子并将其实现到Employee接口。

public  class Cashier implements Employee{
	/*
	     In this class, there are many methods which are not applicable to cashier because
	     it is a leaf node.
	 */
	    private int id;
            private String name;
	    private double salary;
	    public Cashier(int id, String name, double salary)  {
	        this.id=id;
	        this.name = name;
	        this.salary = salary;
	    }
	    @Override
	    public void add(Employee employee) {
	        //this is leaf node so this method is not applicable to this class.
	    }
	    @Override
	    public Employee getChild(int i) {
	        //this is leaf node so this method is not applicable to this class.
	        return null;
	    }
	    @Override
		public int getId() {
			// TODO Auto-generated method stub
			return id;
	    }
	    @Override
	    public String getName() {
	        return name;
	    }
	    @Override
	    public double getSalary() {
	        return salary;
	    }
	    @Override
	    public void print() {
	        System.out.println("==========================");
	        System.out.println("Id ="+getId());
	        System.out.println("Name ="+getName());
	        System.out.println("Salary ="+getSalary());
	        System.out.println("==========================");
	    }
	    @Override
	    public void remove(Employee employee) {
	        //this is leaf node so this method is not applicable to this class.
	    }
}

步骤4

创建一个Accountant类, 该类也将被视为叶子, 并将实现到Employee接口。

public class Accountant implements Employee{
/*
    In this class, there are many methods which are not applicable to cashier because
    it is a leaf node.
*/
    private int id;
    private String name;
    private double salary;
   public Accountant(int id, String name, double salary)  {
   	   this.id=id;
       this.name = name;
       this.salary = salary;
   }
   @Override
   public void add(Employee employee) {
       //this is leaf node so this method is not applicable to this class.
   }
   @Override
   public Employee getChild(int i) {
       //this is leaf node so this method is not applicable to this class.
       return null;
   }
   @Override
	public int getId() {
		// TODO Auto-generated method stub
		return id;
   }
   @Override
   public String getName() {
       return name;
   }
   @Override
   public double getSalary() {
       return salary;
   }
   @Override
   public void print() {
       System.out.println("=========================");
       System.out.println("Id ="+getId());
       System.out.println("Name ="+getName());
       System.out.println("Salary ="+getSalary());
       System.out.println("=========================");
   }
  @Override
   public void remove(Employee employee) {
       //this is leaf node so this method is not applicable to this class.
   }
}

第5步

创建一个CompositePatternDemo类, 该类也将被视为Client, 并且ii将使用Employee接口。

public class CompositePatternDemo {
	public static void main(String args[]){
		 Employee emp1=new Cashier(101, "Sohan Kumar", 20000.0);
		 Employee emp2=new Cashier(102, "Mohan Kumar", 25000.0);
		 Employee emp3=new Accountant(103, "Seema Mahiwal", 30000.0); 
		 Employee manager1=new BankManager(100, "Ashwani Rajput", 100000.0);
		  
		  manager1.add(emp1);
		  manager1.add(emp2);
		  manager1.add(emp3);
		  manager1.print();
        }
}

输出量

==========================
Id =100
Name =Ashwani Rajput
Salary =100000.0
==========================
==========================
Id =101
Name =Sohan Kumar
Salary =20000.0
==========================
==========================
Id =102
Name =Mohan Kumar
Salary =25000.0
==========================
=========================
Id =103
Name =Seema Mahiwal
Salary =30000.0
=========================