02.装饰者模式
2023-02-03 本文已影响0人
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02.装饰者模式
1、认识装饰者模式
购买咖啡时，除了咖啡的各种口味以外，还可以加入各种调料，例如：蒸奶、豆浆、摩卡或奶盖，星巴克会根据加入不同的调料收取不同的费用，当然还有大中小杯等等。
如果我们使用类继承的方式，会导致类数目爆炸、设计死板，以及基类加入的新功能并不适用于所有的子类。
所以我们要采取不一样的做法，我们以饮料为主体，然后采用调料类、体积类来修饰。
（1）拿一个深焙咖啡（DarkRoast）对象
（2）以摩卡（Mocha）对象来修饰
（3）以奶泡（Whip）来修饰
（4）以中杯（Medium）来修饰
（5）调用cost()方法，并依赖委托（delegate）将调料的价钱加上
2、定义
装饰者模式：动态地将责任附加到对象上，若要拓展功能，装饰者提供了比继承更有弹性的替代方案。
BD65E96F-442F-4A17-8CAD-429B18D95F1D_1_105_c.jpeg
3、设计原则：
开放-关闭原则
类应该对扩展开放，对修改关闭。
我们的目标是允许类容易拓展，在不修改现有代码的情况下，就可搭配新的行为。
4、设计
5DC568F8-7135-4D6B-B40D-D48673A49C73_1_201_a.jpeg
代码实现：
（1）装饰者总抽象类
public abstract class Beverage {
public String description = "Unknown Beverage";
public String getDescription(){
return description;
}
public abstract double cost();
}
（2）调料装饰者 抽象类
public abstract class CondimentDecorator extends Beverage {
@Override
public abstract String getDescription();
}
（3）容量装饰者 抽象类
public abstract class Capacity extends Beverage {
@Override
public abstract String getDescription();
}
（4）四种咖啡实现类
/**
* 深度烘焙咖啡类
*/
public class DarkRoast extends Beverage {
public DarkRoast(){
this.description = "DarkRoast";
}
@Override
public double cost() {
return 2.99;
}
}
/**
* 猫屎咖啡
*/
public class Decat extends Beverage {
public Decat(){
this.description = "Decat";
}
@Override
public double cost() {
return 1.89;
}
}
/**
* 浓缩咖啡类
*/
public class Espresso extends Beverage {
public Espresso(){
this.description = "Espresso";
}
@Override
public double cost() {
return 1.99;
}
}
/**
* 首选咖啡（星巴克咖啡名）
*/
public class HouseBlend extends Beverage {
public HouseBlend() {
description = "HouseBlend";
}
@Override
public double cost() {
return 0.89;
}
}
（5）调料类
/**
* 摩卡 调料类
*/
public class Mocha extends CondimentDecorator {
private Beverage beverage;
public Mocha(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ",Mocha";
}
@Override
public double cost() {
return .20 + beverage.cost();
}
}
/**
* 大豆 调料类
*/
public class Soy extends CondimentDecorator {
private Beverage beverage;
public Soy(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ",Soy";
}
@Override
public double cost() {
return .30 + beverage.cost();
}
}
/**
* 鲜奶 调料类
*/
public class Whip extends CondimentDecorator {
private Beverage beverage;
public Whip(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ",Whip";
}
@Override
public double cost() {
return .50 + beverage.cost();
}
}
（6）容量类
/**
* 大杯
*/
public class Big extends Capacity {
private Beverage beverage;
public Big(Beverage beverage){
this.beverage = beverage;
}
@Override
public double cost() {
return beverage.cost() + 0.20;
}
@Override
public String getDescription() {
return beverage.getDescription() + " ,Big";
}
}
/**
* 中杯
*/
public class Medium extends Capacity {
private Beverage beverage;
public Medium(Beverage beverage){
this.beverage = beverage;
}
@Override
public double cost() {
return beverage.cost() + 0.15;
}
@Override
public String getDescription() {
return this.beverage.getDescription() + " ,Medium";
}
}
/**
* 小杯
*/
public class Small extends Capacity {
private Beverage beverage;
public Small(Beverage beverage){
this.beverage = beverage;
}
@Override
public double cost() {
return beverage.cost() + 0.10;
}
@Override
public String getDescription() {
return this.beverage.getDescription() + " ,Small";
}
}
（7）测试类
public class StarbuzzCoffee {
public static void main(String[] args) {
Beverage beverage = new Espresso();
System.out.println(beverage.getDescription() + " $" + beverage.cost());
Beverage beverage1 = new DarkRoast();
beverage1 = new Mocha(beverage1);
beverage1 = new Mocha(beverage1);
beverage1 = new Whip(beverage1);
System.out.println(beverage1.getDescription() + " $" + beverage1.cost());
Beverage beverage2 = new HouseBlend();
beverage2 = new Soy(beverage2);
beverage2 = new Mocha(beverage2);
beverage2 = new Whip(beverage2);
beverage2 = new Big(beverage2);
System.out.println(beverage2.getDescription() + " $" + beverage2.cost());
}
}
结果：
Espresso $1.99
DarkRoast,Mocha,Mocha,Whip $3.8900000000000006
HouseBlend,Soy,Mocha,Whip ,Big $2.09
1、认识装饰者模式
购买咖啡时，除了咖啡的各种口味以外，还可以加入各种调料，例如：蒸奶、豆浆、摩卡或奶盖，星巴克会根据加入不同的调料收取不同的费用，当然还有大中小杯等等。
如果我们使用类继承的方式，会导致类数目爆炸、设计死板，以及基类加入的新功能并不适用于所有的子类。
所以我们要采取不一样的做法，我们以饮料为主体，然后采用调料类、体积类来修饰。
（1）拿一个深焙咖啡（DarkRoast）对象
（2）以摩卡（Mocha）对象来修饰
（3）以奶泡（Whip）来修饰
（4）以中杯（Medium）来修饰
（5）调用cost()方法，并依赖委托（delegate）将调料的价钱加上
2、定义
装饰者模式：动态地将责任附加到对象上，若要拓展功能，装饰者提供了比继承更有弹性的替代方案。
BD65E96F-442F-4A17-8CAD-429B18D95F1D_1_105_c.jpeg
3、设计原则：
开放-关闭原则
类应该对扩展开放，对修改关闭。
我们的目标是允许类容易拓展，在不修改现有代码的情况下，就可搭配新的行为。
4、设计
5DC568F8-7135-4D6B-B40D-D48673A49C73_1_201_a.jpeg
代码实现：
（1）装饰者总抽象类
public abstract class Beverage {
public String description = "Unknown Beverage";
public String getDescription(){
return description;
}
public abstract double cost();
}
（2）调料装饰者 抽象类
public abstract class CondimentDecorator extends Beverage {
@Override
public abstract String getDescription();
}
（3）容量装饰者 抽象类
public abstract class Capacity extends Beverage {
@Override
public abstract String getDescription();
}
（4）四种咖啡实现类
/**
* 深度烘焙咖啡类
*/
public class DarkRoast extends Beverage {
public DarkRoast(){
this.description = "DarkRoast";
}
@Override
public double cost() {
return 2.99;
}
}
/**
* 猫屎咖啡
*/
public class Decat extends Beverage {
public Decat(){
this.description = "Decat";
}
@Override
public double cost() {
return 1.89;
}
}
/**
* 浓缩咖啡类
*/
public class Espresso extends Beverage {
public Espresso(){
this.description = "Espresso";
}
@Override
public double cost() {
return 1.99;
}
}
/**
* 首选咖啡（星巴克咖啡名）
*/
public class HouseBlend extends Beverage {
public HouseBlend() {
description = "HouseBlend";
}
@Override
public double cost() {
return 0.89;
}
}
（5）调料类
/**
* 摩卡 调料类
*/
public class Mocha extends CondimentDecorator {
private Beverage beverage;
public Mocha(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ",Mocha";
}
@Override
public double cost() {
return .20 + beverage.cost();
}
}
/**
* 大豆 调料类
*/
public class Soy extends CondimentDecorator {
private Beverage beverage;
public Soy(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ",Soy";
}
@Override
public double cost() {
return .30 + beverage.cost();
}
}
/**
* 鲜奶 调料类
*/
public class Whip extends CondimentDecorator {
private Beverage beverage;
public Whip(Beverage beverage){
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ",Whip";
}
@Override
public double cost() {
return .50 + beverage.cost();
}
}
（6）容量类
/**
* 大杯
*/
public class Big extends Capacity {
private Beverage beverage;
public Big(Beverage beverage){
this.beverage = beverage;
}
@Override
public double cost() {
return beverage.cost() + 0.20;
}
@Override
public String getDescription() {
return beverage.getDescription() + " ,Big";
}
}
/**
* 中杯
*/
public class Medium extends Capacity {
private Beverage beverage;
public Medium(Beverage beverage){
this.beverage = beverage;
}
@Override
public double cost() {
return beverage.cost() + 0.15;
}
@Override
public String getDescription() {
return this.beverage.getDescription() + " ,Medium";
}
}
/**
* 小杯
*/
public class Small extends Capacity {
private Beverage beverage;
public Small(Beverage beverage){
this.beverage = beverage;
}
@Override
public double cost() {
return beverage.cost() + 0.10;
}
@Override
public String getDescription() {
return this.beverage.getDescription() + " ,Small";
}
}
（7）测试类
public class StarbuzzCoffee {
public static void main(String[] args) {
Beverage beverage = new Espresso();
System.out.println(beverage.getDescription() + " $" + beverage.cost());
Beverage beverage1 = new DarkRoast();
beverage1 = new Mocha(beverage1);
beverage1 = new Mocha(beverage1);
beverage1 = new Whip(beverage1);
System.out.println(beverage1.getDescription() + " $" + beverage1.cost());
Beverage beverage2 = new HouseBlend();
beverage2 = new Soy(beverage2);
beverage2 = new Mocha(beverage2);
beverage2 = new Whip(beverage2);
beverage2 = new Big(beverage2);
System.out.println(beverage2.getDescription() + " $" + beverage2.cost());
}
}
结果：
Espresso $1.99
DarkRoast,Mocha,Mocha,Whip $3.8900000000000006
HouseBlend,Soy,Mocha,Whip ,Big $2.09
