装饰器模式

一.装饰器模式

1.1 定义

• 在不改变原类文件和使用继承的情况下，动态的扩展一个对象的功能.
• 通过创建一个包装对象（装饰），来包裹真实的对象.

二.具体实现

1.1 创建被装饰对象接口

public interface IDecorated {        void print();    }

1.2 创建被装饰对象

public class Decorated implements IDecorated{        @Override        public void print() {            System.out.println("decorated print ...");        }    }

1.3 创建装饰器抽象类

public abstract class Decorator implements IDecorated {        private IDecorated decorated;        public Decorator(IDecorated decorated){            this.decorated = decorated;        }        public void print(){            decorated.print();        }    }

1.4 创建具体装饰器

public class DecoratorA extends Decorator{        public DecoratorA(IDecorated decorated){            super(decorated);        }        @Override        public void print() {            super.print();            System.out.println("decoratorA print ...");        }    }    public class DecoratorB extends Decorator{        public DecoratorB(IDecorated decorated){            super(decorated);        }        @Override        public void print() {            super.print();            System.out.println("decoratorB print ...");        }    }

1.5 调用

public static void main(String[] args) {        IDecorated decorated = new Decorated();        Decorator decorator = new DecoratorA(decorated);        decorator.print();        decorator = new DecoratorB(new DecoratorA(decorated));        decorator.print();    }

1.6 输出

decorated print ...    decoratorA print ...    decorated print ...    decoratorA print ...    decoratorB print ...

三.优缺点

3.1 优点

• 装饰器模式和继承的共同特点就是扩展对象的功能，而装饰器模式比继承更加灵活.
• 通过使用不同的具体装饰器类，及其不同的排列组合，可以产生出大量不同的组合.

3.2 缺点

• 装饰器模式比继承更加复杂.
• 会出现一些小类，过度使用会使程序变得复杂.

四.源码

https://github.com/Seasons20/DisignPattern.git

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