设计模式之——简单工厂设计模式

        简单工厂模式严格意义上不是一种设计模式，它是工厂设计模式的一个特殊实现，又称为静态工厂方法模式，说白了就是由一个工厂对象决定创建出哪一种产品类的实例。一个是工厂类Creator负责生产产品的逻辑判断，一个是产品接口（或者抽象类）IProduct定义了产品通用的属性/操作，为了使工厂类能够知道我们需要哪一种产品，我们需要在创建产品时传递给工厂类一个参数，去表明我们想要创建哪种产品。下面是范例：

        举个栗子，如果我们想写一个计算器，首先写出了加法运算，然后又想写一个减法......这么多运算如果扩展起来维护肯定捉襟见肘。所以我们考虑，这些都是运算，我定义一个抽象类Operation,里面直接返回运算的结果，具体如何实现的由实现它的子类具体实现，然后定义一个生产运算的工厂，当需要什么运算给工厂发送个信号生产出相应的运算。这样如果新的运算扩展只需要继承“运算”类，自己该怎么实现就怎么实现，各个运算间互不影响，维护起来也方便。

运算抽象类Operation

package com.zndroid.dm.FactoryModel.EasyFactory;

/**
* Created by luzhenyu on 2016/8/15.
*/
public abstract class Operation {
protected double numA;
protected double numB;

public void setNumA(double numA) {
this.numA = numA;
}

public void setNumB(double numB) {
this.numB = numB;
}

public abstract double getResult();
}

具体运算实现

package com.zndroid.dm.FactoryModel.EasyFactory.impl;

import com.zndroid.dm.FactoryModel.EasyFactory.Operation;

/**
* Created by luzhenyu on 2016/8/15.
*/
public class AddOperator extends Operation {

@Override
public double getResult() {
return numA + numB;
}
}

package com.zndroid.dm.FactoryModel.EasyFactory.impl;

import com.zndroid.dm.FactoryModel.EasyFactory.Operation;

/**
* Created by luzhenyu on 2016/8/15.
*/
public class DivisionOperator extends Operation {
@Override
public double getResult() {
return numA / numB;
}
}

运算工厂Factory

package com.zndroid.dm.FactoryModel.EasyFactory;

import com.zndroid.dm.FactoryModel.EasyFactory.impl.AddOperator;
import com.zndroid.dm.FactoryModel.EasyFactory.impl.DivisionOperator;

/**
* Created by luzhenyu on 2016/8/13.
*/
public class Easyfactory {
public static Operation createOperation (String operator) {
Operation mOpration = null;

if ("".equals(operator) || null == operator)
return null;

switch (operator){
case "+":
mOpration = new AddOperator();
break;
case "/":
mOpration = new DivisionOperator();
break;
}

return mOpration;
}
}

使用：

package com.lzy.zndroid;

import com.zndroid.dm.FactoryModel.EasyFactory.Easyfactory;
import com.zndroid.dm.FactoryModel.EasyFactory.Operation;
import com.zndroid.dm.SingletonModel.SingletonModel;

public class Demo {
public static void main(String[] args){
log("========================================");

SingletonModel s1 = SingletonModel.getInstance();

SingletonModel s2 = SingletonModel.getInstance();

log("" + (s1 == s2));
log("----------------我是分割线-----------------");

Operation addOperator = Easyfactory.createOperation("+");
addOperator.setNumA(100);
addOperator.setNumB(150);
log(addOperator.getResult() + "");

Operation divisionOperator = Easyfactory.createOperation("/");
divisionOperator.setNumA(888);
divisionOperator.setNumB(4);
//Demo暂时不考虑被除数为“0”的情况
log(divisionOperator.getResult() + "");
log("----------------我是分割线-----------------");

log("========================================");
}

private static void log(String msg) {
System.out.println("[ " + msg + " ]");
}
}

总闻到一点不好的味道，代码出现在哪里呢？
【欢迎上码】
【微信公众号搜索 h2o2s2】