今天学习了简单工厂模式，总结一下。

　　　　简单工厂模式的核心思想是：由一个工厂实体决定创建出哪一种产品的实例。

　　　　比较简单，因此直接上代码：

    这个例子我们实现一个简单的计算器。我们先定义一个计算行为接口，行为比较简单就是计算。

1 package com.java.simpleFactory;2 3 public interface CalcOperation {4     public float doCalc();5 }

接着我们分别用加减乘除不同的运算去实现这个接口。

1 package com.java.simpleFactory; 2  3 public class AddOperation extends DefaultOperation implements CalcOperation{ 4      5     public AddOperation(float a,float b){ 6         this.setA(a); 7         this.setB(b); 8     } 9     10     @Override11     public float doCalc() {12         return this.getA()+this.getB();13     }14 15 }16 17 18 package com.java.simpleFactory;19 20 public class MinusOperation extends DefaultOperation implements CalcOperation {21     22     public MinusOperation(float a,float b) {23         this.setA(a);24         this.setB(b);25     }26     27     28     @Override29     public float doCalc() {30         return this.getA()-this.getB();31     }32 33 }34 35 package com.java.simpleFactory;36 37 public class MultOperation extends DefaultOperation implements CalcOperation {38 39     public MultOperation(float a,float b) {40         this.setA(a);41         this.setB(b);42     }43 44     @Override45     public float doCalc() {46         return this.getA()*this.getB();47     }48 49 }50 51 package com.java.simpleFactory;52 53 public class DvdOperation extends DefaultOperation implements CalcOperation {54 55     public DvdOperation(float a,float b) {56         this.setA(a);57         this.setB(b);58     }59 60     @Override61     public float doCalc() {62         if(this.getB()==0)63             return 0;64         return this.getA()/this.getB();65     }66 67 }

最后就是我们的工厂类了

1 package com.java.simpleFactory; 2  3 public class OperationFactory { 4  5     public CalcOperation CreateOpreation(String sign,float a,float b){ 6         CalcOperation calcOperation = null; 7         switch(sign){ 8             case "+": 9                 calcOperation = new AddOperation(a, b);10                 break;11             case "-":12                 calcOperation = new MinusOperation(a, b);13                 break;14             case "*":15                 calcOperation = new MultOperation(a, b);16                 break;17             case "/":18                 calcOperation = new DvdOperation(a, b);19                 break;20         }21         return calcOperation;22     }23 24 }

测试一下

1 package com.java.simpleFactory; 2  3 public class Test { 4  5     public static void main(String[] args) { 6         OperationFactory factory=new OperationFactory(); 7         CalcOperation operation = factory.CreateOpreation("/", 2, 3); 8         System.out.println(operation.doCalc()); 9 10     }11 12 }

简单工厂模式看着很简单，但是作用很大。推荐大佬的一片文章：http://www.cnblogs.com/zuoxiaolong/p/pattern4.html