做出来的软件具有很强的扩展性,扩展并不是修改以前的源代码,而是在以前的代码之外添加新的功能.

重点是对扩展开放,对修改关闭.

银行业务员下有很多子类:负责存款的银行业务员,负责取款的银行业务员,负责转账的银行业务员.

Client是进行模块的调用,不算模块的修改.除了客户端MainClass之外,其他都是模块:BankWorker、DrawingBankWorker、JiJinBankWorker、SavingBankWorker、zhuanzhangBankWorker

仅仅是通过添加子类就实现了功能的扩展.

特别是最重要的抽象模块不能再修改,就是这里的BankWorker模块没有再修改.接口是一定不要修改的,否则它的所有的实现子类都要修改.如果接口中的方法被修改了,Client中的调用接口的方法都会受到影响.所以最重要是抽象模块不能被修改.

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/* * 银行业务员 *  */public class BankWorker {    //负责存款业务    public void saving() {        System.out.println("进行存款操作");            }    //负责取款业务    public void drawing(){        System.out.println("进行取款操作");    }        //负责转账业务    public void zhuanzhang(){        System.out.println("进行转账操作");    }    //负责基金的申购    public void jijin(){        System.out.println("进行基金申购操作");    }}

public class MainClass {     public static void main(String[] args) {        BankWorker bankWorker = new BankWorker();                //存款        bankWorker.saving();                //取款        bankWorker.drawing();                //转账业务        bankWorker.zhuanzhang();                //负责基金采购        bankWorker.jijin();    }}

package com.ibeifeng.ex2;/* * 银行业务员接口,是所有业务员的抽象父类 *  */public interface BankWorker {      public void operation();}

package com.ibeifeng.ex2;/* * 负责取款业务的业务员 *  *  */public class DrawingBankWorker implements BankWorker{    @Override    public void operation() {        // TODO Auto-generated method stub        System.out.println("进行取款操作");    }}

package com.ibeifeng.ex2;public class JiJinBankWorker implements BankWorker {    @Override    public void operation() {        // TODO Auto-generated method stub       System.out.println("进行基金申购操作");    }}

package com.ibeifeng.ex2;public class MainClass {    public static void main(String[] args) {        BankWorker bankWorker = new SavingBankWorker();        bankWorker.operation();                BankWorker bankWorker2 =  new DrawingBankWorker();        bankWorker2.operation();                BankWorker bankWorker3 = new zhuanzhangBankWorker();        bankWorker3.operation();                BankWorker bankWorker4  = new JiJinBankWorker();        bankWorker4.operation();    }}

package com.ibeifeng.ex2;/* * 负责存款的业务员 *  */public class SavingBankWorker implements BankWorker {    @Override    public void operation() {        // TODO Auto-generated method stub        System.out.println("进行存款操作");    }     }

package com.ibeifeng.ex2;/* * 负责转账业务的银行业务员 *  */public class zhuanzhangBankWorker implements BankWorker{    @Override    public void operation() {        // TODO Auto-generated method stub        System.out.println("进行转账操作");    }}