（转) java 简单工厂模式（实现一个计算器）

package com.simpleFactory;

/**
 * 运算类
 * @author Administrator
 *
 */
public class Operation {

    private double numberA;

    private double numberB;

    public double getResultValue(){
        return 0.0;
    }

    public double getNumberA() {
        return numberA;
    }

    public void setNumberA(double numberA) {
        this.numberA = numberA;
    }

    public double getNumberB() {
        return numberB;
    }

    public void setNumberB(double numberB) {
        this.numberB = numberB;
    }

}

package com.simpleFactory;

/**
 * 加法实现方式
 * @author Administrator
 *
 */
public class Addition extends Operation {

    @Override
    public double getResultValue() {
        return getNumberA() + getNumberB();
    }
}

package com.simpleFactory;

/**
 * 减法实现方式
 * @author Administrator
 *
 */
public class Subtracter extends Operation {

    @Override
    public double getResultValue() {
        return getNumberA() - getNumberB();
    }
}

package com.simpleFactory;

/**
 * 简单工厂类
 * @author Administrator
 *
 */
public class SimpleFactory {

    private Operation operation;
    public Operation factoryOperate (String type ){

        if ("+".equals(type)){

            operation = new Addition();
        }
        else if ("-".equals(type)){

            operation = new Subtracter();
        }
     return operation;
    }
}

package com.simpleFactory;

/**
 * 简单工厂类 ,利用反射实现
 * @author Administrator
 *
 */
public class SimpleFactory_reflect {

    private Operation operation;
    public Operation factoryOperate (String classType ){

         try {
        operation = (Operation)Class.forName("com.simpleFactory."+classType).newInstance();
        } catch (Exception e) {

            e.printStackTrace();
        }

     return operation;
    }
}

重点的是在反射这里，通过反射机制可以不要在增加新功能时修改工厂类，只需要将新的方法函数名加进去就可以了。