装饰模式

动态的将责任附加到对象上。若要扩展功能，装饰者提供了比继承更有弹性的取代方案

代码

package gx.component;/** * 组件：装饰类和被装饰类 都要继承：为了类型保持一致 * @author always * */public abstract class Component {
          public abstract void description();    public abstract int cost();}

package gx.component.impl;import gx.component.Component;/** * 装饰类的抽象类 * @author always * */public abstract class  Decorator extends Component{
          protected Component component;}

package gx.component.impl;import gx.component.Component;/** *  * 被包装的类 * @author always * */public class Phone extends Component{
          public void description() {        System.out.println("裸机");    }    public int cost() {        return 1900;    }}

package gx.decorator.impl;import gx.component.Component;import gx.component.impl.Decorator;/** *  * 装饰1：给手机买个壳 * @author always * */public class DaiKe extends Decorator{
          public DaiKe(){    }    public DaiKe(Component component){        this.component=component;    }    public void description() {        this.component.description();        System.out.println("带了手机壳");    }    public int cost() {        return 50+this.component.cost();    }}

package gx.decorator.impl;import gx.component.Component;import gx.component.impl.Decorator;/** *  * 装饰2：给手机贴个膜 * @author always * */public class TieMo extends Decorator{
          public TieMo(){}    public TieMo(Component component){        this.component=component;    }    public void description() {        this.component.description();        System.out.println("贴了膜");    }    public int cost() {        return 20+this.component.cost();    }}

測试类：

package gx;import gx.component.Component;import gx.component.impl.Phone;import gx.decorator.impl.DaiKe;import gx.decorator.impl.TieMo;import junit.framework.TestCase;public class TestDecorator extends TestCase {
          public void testDecorator() {        Component component = new TieMo(new DaiKe(new Phone()));        component.description();        System.out.println("价钱：" + component.cost());        /*         * 结果：         *  裸机          *  带了手机壳         *  贴了膜          *  价钱：1970         */    }}