设计模式2--装饰模式（the decorator design pattern）

怼烎@ 2024-02-17 16:12 33阅读 0赞

允许多次实现一种方法，避免每次改动代码。

没有使用装饰模式：

Computer description()  
Computer new\_description()  
Computer newer\_description()  
  
使用了装饰模式：  
  
Computer description()  
  
  
Computer description()  
Disk description()  
  
  
Computer description()  
Disk description()  
Monitor description()

public class Computer
    {
    	public Computer(){}
    	
    	public String description() {
    		return "You're getting a computer.";
    	}
    }
    
    public class Computer
    {
    	public Computer(){}
    	
    	public String description() {
    		return "You're getting a computer and a disk.";
    	}
    }
    
    public class Computer
    {
    	public Computer(){}
    	
    	public String description() {
    		return "You're getting a computer and a disk and a monitor.";
    	}
    }
    
    
    public class Computer
    {
    	public Computer(){}
    	
    	public String description() {
    		return "computer";
    	}
    }
    
    public abstract class ComponentDecorator extends Computer
    {
    	public abstract String description();
    }
    
    public class Disk extends ComponentDecorator
    {
    	Computer computer;
    	
    	public Disk(Computer c)
    	{
    		computer = c;
    	}
    	
    	public String description()
    	{
    		return computer.description()+" and a disk";
    	}
    }
    
    public class Monitor extends ComponentDecorator
    {
    	Computer computer;
    	
    	public Monitor(Computer c)
    	{
    		computer = c;
    	}
    	
    	public String description()
    	{
    		return computer.description()+" and a monitor";
    	}
    }
    
    public class Test
    {
    	public static void main(String args[]) {
    		Computer computer = new Computer();
    		computer = new Disk(computer);
    		computer = new Monitor(computer);
    		computer = new Monitor(computer);
    		System.out.println("You're getting a " + computer.description() + ".");	
    	}
    }