设计模式之简单工厂模式

　　　　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     @Override
11     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     @Override
29     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     @Override
45     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     @Override
61     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