JAVA实现装饰模式

环境：汽车4s店汽车销售，出售奥迪A1，A4，A6。可装饰的组件有倒车雷达，真皮座椅，GPS定位。有一辆裸车，要实现对裸车的装饰
分析：买车的人需求各不一样，有的人要奥迪A1装有雷达、GPS，有的人要奥迪A4装有真皮座椅、GPS等等。如果你把所有的可能情况都例举出来，就会出现“类爆炸”的现象，显然这是不合理的。
问题：动态的给一个对象添加一些功能扩展
解决方案：装饰模式
角色：装饰者
被装饰者

Car.java

public abstract class Car {
protected int cost;
protected String description;
public abstract String getDescription();
public abstract int getCost();
}

A1Car.java

public class A1Car extends Car{
public A1Car()
{
  cost = 100000;
  description = "Audi A1 Car";
}
@Override
public int getCost() {
  return cost;
}
@Override
public String getDescription() {
  return description;
}
}

A4Car.java

public class A4Car extends Car{
public A4Car()
{
  cost = 120000;
  description = "Audi A4 Car";
}
@Override
public int getCost() {
  return cost;
}
@Override
public String getDescription() {
  return description;
}
}

Decorator.java

public class Decorator extends Car{
protected Car c;
protected int decoratorcost;
protected String decoratordescription;
public void setCar(Car a){
  c = a;
}
@Override
public int getCost() {
  return decoratorcost+c.getCost();
}
@Override
public String getDescription() {
  return decoratordescription+c.getDescription();
}
}

GPS.java

public class Gps extends Decorator{
public Gps(){
decoratorcost=500;
decoratordescription="with GPS";
}
}

Radar.java

public class Radar extends Decorator{
public Radar(){
decoratorcost=1500;
decoratordescription="with Radar";
}
}

Test.java

public class Test {
public static void main(String[] args) {
  //给奥迪A1装配GPS
  Car a1 = new A1Car();
  Decorator decorator = new Gps();
  decorator.setCar(a1);
  System.out.println(a1.getDescription()+"的价格是"+a1.getCost());
  System.out.println(decorator.getDescription()+"的价格是"+decorator.getCost());
  //想再给A1装配Radar，由于装饰者与被装饰者具有相同的类型，我们可以用装饰后的对象代替原来的对象
  Decorator decorator2 = new Radar();
  decorator2.setCar(decorator);
  System.out.println(decorator2.getDescription()+"的价格是"+decorator2.getCost());
}
}

运行结果

Audi A1 Car的价格是100000
with GPS Audi A1 Car的价格是100500
with Radar with GPS Audi A1 Car的价格是102000

在Java I/O库中输入输出流的设计模式就使用了装饰模式

如Reader

项目中，我们经常这样写

FileReader fr = new FileReader("d:\\myDoc\\test.txt");

BufferedReader br = new BufferedReader(fr);//这里接收一个Reader类型参数

BufferedReader相当于装饰者，而Reader及其子类都可以作为被装饰者

猜你喜欢