设计形式-装饰模式

设计模式--装饰模式
  Decorator定义:
动态给一个对象添加一些额外的职责,就象在墙上刷油漆.使用Decorator模式相比用生成子类方式达到功能的扩充显得更为灵活.
  为什么使用Decorator?
我们通常可以使用继承来实现功能的拓展,如果这些需要拓展的功能的种类很繁多,那么势必生成很多子类,增加系统的复杂性,同时,使用继承实现功能拓展,我们必须可预见这些拓展功能,这些功能是编译时就确定了,是静态的.

  使用Decorator的理由是:这些功能需要由用户动态决定加入的方式和时机.Decorator提供了"即插即用"的方法,在运行期间决定何时增加何种功能.

package Decorator;public abstract class SchoolReport {public abstract void report();public abstract void sign(String name);}

package Decorator;public abstract class Decorator extends SchoolReport {private SchoolReport report;public Decorator(SchoolReport report) {super();this.report = report;}public void report() {this.report.report();}public void sign(String name) {this.report.sign(name);}}

package Decorator;public class FouthGradeSchoolReport extends SchoolReport {@Overridepublic void report() {System.out.println("ok");}@Overridepublic void sign(String name) {System.out.println(name + "--");}}

package Decorator;public class HighSchoolDecorator extends Decorator {public HighSchoolDecorator(SchoolReport report) {super(report);}private void reportHighScore() {System.out.println("装饰后的");}@Overridepublic void report() {this.reportHighScore();super.report();}}

package Decorator;public class SortDecorator extends Decorator {public SortDecorator(SchoolReport report) {super(report);}private void peportSort() {System.out.println("装饰排名");}@Overridepublic void report() {super.report();this.peportSort();}}

package Decorator;public class Client {public static void main(String[] args) {SchoolReport report;report=new FouthGradeSchoolReport();report=new HighSchoolDecorator(report);report=new SortDecorator(report);report.report();report.sign("pass");}}