装饰模式（Decorator Pattern）_public class concretedecorator extends decorator {-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_26880671/article/details/83964775

本文介绍装饰模式，一种通过包装对象来扩展其功能的设计模式。它提供了一种替代继承的方法，允许在运行时动态地给对象添加职责。文中给出了装饰模式的基本结构、Java实现代码示例及其适用场景。

装饰模式又名包装（Wrapper）模式。装饰模式以对客户透明的方式扩展对象的功能，是继承关系的一个替代方案。
类图：

示例：
装饰模式使用原来被装饰的类的一个子类的实例，把客户端的调用委派到被装饰类。装饰模式的关键在于这种扩展时完全透明的。
1、模式的结构：

2、java代码

Component类:

package decorator;

public interface Component {
public void sampleOperation();
}

ConcreteComponent类:

package decorator;

public class ConcreteComponent implements Component{

public ConcreteComponent(){
System.out.println("ConcreteComponent。。。。。。");
}
public void sampleOperation() {
System.out.println("ConcreteComponent operate。。。。。。");
}
}

Decorator类：

package decorator.decorator;

import decorator.Component;

public class Decorator implements Component{
private Component component;
public Decorator(Component c){
  super();
  component = c;
}
public Decorator(){
  System.out.println("Decorator。。。。。。");
}
public void sampleOperation() {
  component.sampleOperation();
}
}

DecoratorComponent类：

package decorator.decorator;

import decorator.Component;
public class ConcreteDecorator1 extends Decorator {

public ConcreteDecorator1(){
  System.out.println("ConcreteDecorator1。。。。。。");
}
public ConcreteDecorator1(Component c){
  super(c);
}
public void sampleOperation() {
  super.sampleOperation();
  System.out.println("ConcreteDecorator1 operate。。。。。。");
}
}

package decorator.decorator;

import decorator.Component;
public class ConcreteDecorator2 extends Decorator {

public ConcreteDecorator2(){
  System.out.println("ConcreteDecorator2。。。。。。");
}
public ConcreteDecorator2(Component c){
  super(c);
}
public void sampleOperation() {
  super.sampleOperation();
  System.out.println("ConcreteDecorator2 operate。。。。。。");
}
}

Client类：

package decorator;
import decorator.decorator.ConcreteDecorator1;
import decorator.decorator.ConcreteDecorator2;
public class Client {

public static void main(String args[]){
  Component a = new ConcreteComponent();
  Component decorator1 = new ConcreteDecorator1(a);
  Component decorator2 = new ConcreteDecorator2(decorator1);
  decorator2.sampleOperation();
}
}

装饰模式应当在什么情况下使用：