栗子回顾

简单工厂模式：
https://www.cnblogs.com/call-me-devil/p/10926633.html

运算类使用工厂方法模式实现

UML图

代码实现

工厂接口

/**
 * 工厂接口
 * Created by callmeDevil on 2019/7/7.
 */
public interface IFactory {
    /**
     * 创建运算类
     *
     * @return
     */
    BaseOperation createOpertaion();
}

运算基础类

为节省篇章，详见简单工厂模式，此处省略。
以下加减乘除运算类(OperationAdd、OperationSub、OperationMul、OperationDiv)同。

加法工厂

/**
 * 加法工厂
 * Created by callmeDevil on 2019/7/7.
 */
public class AddFactory implements IFactory{
    @Override
    public BaseOperation createOpertaion() {
        return new OperationAdd();
    }
}

减法工厂

/**
 * 减法工厂
 * Created by callmeDevil on 2019/7/7.
 */
public class SubFactory implements IFactory {
    @Override
    public BaseOperation createOpertaion() {
        return new OperationSub();
    }
}

乘法工厂

/**
 * 乘法工厂
 * Created by callmeDevil on 2019/7/7.
 */
public class MulFactory implements IFactory{
    @Override
    public BaseOperation createOpertaion() {
        return new OperationMul();
    }
}

除法工厂

/**
 * 除法工厂
 * Created by callmeDevil on 2019/7/7.
 */
public class DivFactory implements IFactory{
    @Override
    public BaseOperation createOpertaion() {
        return new OperationDiv();
    }
}

测试

/**
 * 工厂方法模式测试
 * Created by callmeDevil on 2019/7/7.
 */
public class Test {
    public static void main(String[] args) {
        IFactory operFactory = new AddFactory();
        BaseOperation oper = operFactory.createOpertaion();
        oper.setNumA(1);
        oper.setNumB(2);
        double result = oper.getResult();
        System.out.println("加法测试结果：" + result);
    }
}