简单工厂模式

业务的封装：让业务逻辑和界面逻辑分开，让他们之间的耦合度下降，只有分离开，才能达到容易维护或扩展。

简单工厂模式：用一个单独的类来做创建实例的过程，这就是工厂。

以简单的计算器为例，介绍简单工厂模式。

创建一个Operation类

public  class Operation {private double numA;private double numB;public double getNumA() {return numA;}public void setNumA(double numA) {this.numA = numA;}public double getNumB() {return numB;}public void setNumB(double numB) {this.numB = numB;}public double Result(){return 0;};}

加、减、乘、除，都继承自operation，并重写Result方法。

加法

public class OperationAdd extends Operation{@Overridepublic double Result() {return getNumA()+getNumB();}}

减法

public class OperationSub extends Operation{@Overridepublic double Result() {return getNumA()-getNumB();}}

乘法

public class OperationMul extends Operation{@Overridepublic double Result() {return getNumA()*getNumB();}}

除法

public class OperationDiv extends Operation{@Overridepublic double Result() {    int result=0;if(getNumB()==0){System.out.println("除数不为0");}else {return getNumA()/getNumB();}return result;}}

工厂类

//工厂类public class OperationFactory {public static Operation createOperation(String state){Operation oper=null;switch (state) {case "+":oper=new OperationAdd();break;case "-":oper=new OperationSub();break;case "*":oper=new OperationMul();break;case "/":oper=new OperationDiv();break;default:break;}return oper;}}

客户端代码

public class client {public static void main(String[] args) {Operation oper1 = null;oper1=OperationFactory.createOperation("/");oper1.setNumA(10);oper1.setNumB(5);double result=oper1.Result();System.out.println(result);}}

当我们需要增加其他运算时，只需要增加相应的运算子类，并在运算类工厂中增加分支即可。

同时，界面显示和我们的业务逻辑也是分离的～

参考博客：http://blog.csdn.net/jiange_zh/article/details/50174001