工厂模式（Factory Method）

工厂设计模式：通过面向对象的三大特性（封装、继承、多态）定义一个用于创建对象的接口，让子类决定实例化那个类，工厂方法使一个类的实例化延迟到其子类

简单案例（加法计算器）

//加减乘除操作工厂

public interface OperationInterface {    public double operate(int a,int b);}

//创建加减乘除的工厂

public interface FactoryInteface{    public OperationInterface CreateFactory();}

//加法操作类

public class OperationAdd implements OperationInterface {    @Override    public double operate(int a, int b) {        return a+b;    }    }

//创建加法这一操作的工厂

public class FactoryAdd implements FactoryInteface{    @Override    public OperationInterface CreateFactory() {        return new OperationAdd();    }}

//主函数调用

public class Factory {    public static void main(String[] arg)    {        FactoryAdd factoryAdd = new FactoryAdd();        OperationInterface add =  factoryAdd.CreateFactory();        System.out.println(add.operate(23, 123));    }}