工厂方法模式

解释

工厂方法模式:定义一个用于创建对象的接口,让子类决定实例化哪一个类,工厂方法使一个类的实例化延期到其子类.
工厂模式的优点,克服了简单工厂违背开放-封闭原则(对扩展开放对更改封闭)的缺点
当然存在不足,新增一个产品就要增加一个产品的工厂类,增加了额外的开发量.

具体代码

抽象工厂

public interface IFactory {
    Operation CreateOperation();
}

具体的工厂,加减乘除工厂

class AddFactory implements IFactory {


    @Override
    public Operation CreateOperation() {
        return new OperationAdd();
    }

}

class SubFactory implements IFactory {


    @Override
    public Operation CreateOperation() {
        return new OperationSub();
    }

}

class MulFactory implements IFactory {


    @Override
    public Operation CreateOperation() {
        return new OperationMul();
    }

}

class DivFactory implements IFactory {


    @Override
    public Operation CreateOperation() {
        return new OperationDiv();
    }

}

运算符类

public abstract class Operation {
    private double nA = 0;
    private double nB = 0;

    public void setnA(double nA) {
        this.nA = nA;
    }

    public void setnB(double nB) {
        this.nB = nB;
    }

    public double getnA() {
        return nA;
    }

    public double getnB() {
        return nB;
    }

    public abstract double GetRsult();
}

具体产品角色。

class OperationAdd extends Operation {

    @Override
    public double GetRsult() {
        return getnA() + getnB();
    }
}

class OperationSub extends Operation {

    @Override
    public double GetRsult() {
        return getnA() - getnB();
    }
}

class OperationMul extends Operation {

    @Override
    public double GetRsult() {
        return getnA() * getnB();
    }
}

class OperationDiv extends Operation {

    @Override
    public double GetRsult() {
        if (getnB() != 0) {
            return getnA() / getnB();
        }
        return 0;
    }
}

测试类

public class Main {

    public static void main(String[] args) {

        //如果是简单工厂要增加一个新算法例如立方,必须修改工厂类是不合适的
        //工厂模式时候,只需要在客户端修改代码就可以了
        IFactory operF = new AddFactory();

        Operation oper = operF.CreateOperation();
        oper.setnA(2);
        oper.setnB(2);
        System.out.print(oper.GetRsult());
    }
}