定义:在不改变原有对象的基础上,将功能附加到对象自上
提供了比继承更有弹性的替代方案(扩展原有对象功能)
类型:结构型
扩展一个类的功能或给一个类添加附加职责
动态的给一个对象添加功能,这些功能可以再动态的撤销
继承的有力补充,比继承灵活,不改变原有对象的情况下给一个对象扩展功能
通过使用不同装饰类以及这些装饰类的排列组合,可以实现不同效果
缺点:
会出现更多的代码,更多的类,增加程序复杂性
动态装饰时,多层装饰时会更加复杂
public abstract class ABattercake { protected abstract String getDesc();; protected abstract int cost(); }
public class Battercake extends ABattercake { @Override protected String getDesc() { return "jianbing"; } @Override protected int cost() { return 8; } }
public class AbstractDecorator extends ABattercake { private ABattercake aBattercake; public AbstractDecorator (ABattercake aBattercake){ this.aBattercake=aBattercake; } @Override protected String getDesc() { return this.aBattercake.getDesc(); } @Override protected int cost() { return this.aBattercake.cost(); } }
public class EggDecorator extends AbstractDecorator { public EggDecorator(ABattercake aBattercake){ super(aBattercake); } @Override protected String getDesc() { return super.getDesc()+" jiayigejidan"; } @Override protected int cost() { return super.cost()+1; } }
public class SausageDecorator extends AbstractDecorator{ public SausageDecorator(ABattercake aBattercake){ super(aBattercake); } @Override protected String getDesc() { return super.getDesc()+" jiayigenxiangchang"; } @Override protected int cost() { return super.cost()+2; } }
public class Test { public static void main(String[] args) { ABattercake aBattercake; aBattercake=new Battercake(); aBattercake=new EggDecorator(aBattercake); aBattercake=new EggDecorator(aBattercake); aBattercake=new SausageDecorator(aBattercake); System.out.println(aBattercake.getDesc()+""+aBattercake.cost()); } }
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