第二十六讲：基础一开放封闭原则

Posted 2020-09-13 绿茵好莱坞

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");
    }

}