装饰器模式

装饰器模式：动态地为对象添加一些额外的功能。

特点：

1、装饰者和被装饰者拥有相同的超类型，可以是接口可以是抽象类。

2、装饰类中包含一个被装饰类组件的引用

3、可以为被装饰对象添加额外的功能

4、在装饰类中重写被装饰组件类中的方法，并对被装饰组件类中对应的方法调用。

结构图：

1、Component是装饰器模式中公共方法的类，在装饰器模式的顶层。

2、ConcreateComponent是转换器模式中具体被装饰的类，IO包中的媒体流就是此种对象。

3、Decorator 装饰器模式的核心对象，所有具体装饰类对象的父类，完成装饰器的部分职能，继承自Component，同时包含一个Component作为成员变量，装饰器模式中动态添加的功能是在这里实现的。

4、ConcreteDecoratorA和ConcreteDecoratorB是两个具体的装饰器对象，他们完成具体的装饰功能，装饰功能的实现通过调用被装饰对象对应的方法，加上装饰对象自身的方法，这是装饰模式中动态添加额外功能的关键。

/**
 * 所有类的超类
 * @author mcx
 *
 */
public abstract class Ingredient {
   public abstract String getDescription();
   public abstract double getPrice();   
   public void print(){
  System.out.println("name "+this.getDescription());
  System.out.println("price "+this.getPrice());
   }

}

public class Bread extends Ingredient{
private String description;
public Bread(String description){
this.description = description;
}
@Override
public String getDescription() {
return description;
}
@Override
public double getPrice() {
return 3;
}
}

public abstract class Decorator extends Ingredient{
protected Ingredient ingredient;
public Decorator(Ingredient ingredient){
this.ingredient = ingredient;
}
public abstract String getDescription();
public abstract double getPrice();
}

public class Beef extends Decorator{
public Beef(Ingredient ingredient) {
super(ingredient);
}
@Override
public String getDescription() {
return ingredient.getDescription() +" decorated with beef";
}
@Override
public double getPrice() {
double beef = 4;
double bread = ingredient.getPrice();
return bread + beef;
}
}

public class GreenGrocery extends Decorator{
public GreenGrocery(Ingredient ingredient) {
super(ingredient);
}
@Override
public String getDescription() {
return ingredient.getDescription() +" decorated with GreenGrocery";
}
@Override
public double getPrice() {
return ingredient.getPrice() + 2;
}
}

public class Mutton extends Decorator{
public Mutton(Ingredient ingredient) {
super(ingredient);
}
@Override
public String getDescription() {
return ingredient.getDescription() + " decorated with mutton";
}
@Override
public double getPrice() {
return ingredient.getPrice() + 4;
}
}

public class Pork extends Decorator{
public Pork(Ingredient ingredient){
super(ingredient);
}
@Override
public String getDescription() {
return ingredient.getDescription() + " decorated with pork";
}
@Override
public double getPrice() {
return ingredient.getPrice() + 4;
}
}

public class Salard extends Decorator{
public Salard(Ingredient ingredient) {
super(ingredient);
}
@Override
public String getDescription() {
return ingredient.getDescription()+" decorated with salard";
}
@Override
public double getPrice() {
return ingredient.getPrice() + 3;
}
}

public class Test {
public static void main(String[] args) {
 Ingredient sand1 = new Beef(new GreenGrocery(new Bread(" bread with milk")));
  Ingredient sand2 = new Mutton(new Beef(new Pork(new Bread(" bread with cheese"))));
  Ingredient sand3 = new Beef(new Salard(new GreenGrocery(new Bread("bread with milk"))));
  sand1.print();
  sand2.print();
  sand3.print();
}
}