装饰模式指的是在不必改变原类文件和使用继承的情况下，动态地扩展一个对象的功能。它是通过创建一个包装对象，也就是装饰来包裹真实的对象。
public interface ICake {
public float cost();
}
public abstract class CakeDecorator implements ICake{
}
public class MilkCake implements ICake{
@Override
public float cost() {
return 100f;
}
}
public class Berry extends CakeDecorator {
private ICake cake;
public Berry(ICake cake) {
this.cake = cake;
}
@Override
public float cost() {
float berryPrice = 5f;
return cake.cost() + berryPrice;
}
}
public class Chocolate extends CakeDecorator{
private ICake cake;
public Chocolate(ICake cake) {
this.cake = cake;
}
@Override
public float cost() {
float chocolatePrice = 25f;
return cake.cost() + chocolatePrice;
}
}
public class Test {
public static void main(String[] args) throws FileNotFoundException {
MilkCake mc = new MilkCake();
Berry b = new Berry(mc);
Chocolate c = new Chocolate(b);
System.out.println("" + c.cost());
}
}