工厂方法模式（Java代码）

工厂方法模式（Factory Method），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迟到其子类。

运算类：

//运算类
public abstract class Operation {
    private double numberA=0;
    private double numberB=0;
    public double getNumberB() {
        return numberB;
    }
    public void setNumberB(double numberB) {
        this.numberB = numberB;
    }
    public double getNumberA() {
        return numberA;
    }
    public void setNumberA(double numberA) {
        this.numberA = numberA;
    }
    public abstract double GetResult();
}

//加法类
public class OperationAdd extends Operation {
    public double GetResult()
    {
        double result=0;
        result=super.getNumberA()+super.getNumberB();
        return result;
    }
}

//减法类
public class OperationSub extends Operation {
    public double GetResult()
    {
        double result=0;
        result=super.getNumberA()-super.getNumberB();
        return result;
    }
}

//乘法类
public class OperationMul extends Operation {
    public double GetResult()
    {
        double result=0;
        result=super.getNumberA()*super.getNumberB();
        return result;
    }
}

//除法类
public class OperationDiv extends Operation {
    public double GetResult()
    {
        double result=0;
        result=super.getNumberA()/super.getNumberB();
        return result;
    }
}

先创建一个工厂接口：

public interface IFactory {
    Operation CreateOperation();
}

然后加减乘除各建一个具体工厂去实现这个接口：

public class AddFactory implements IFactory {
    public Operation CreateOperation()
    {
        return new OperationAdd();
    }
}

public class SubFactory implements IFactory {
    public Operation CreateOperation()
    {
        return new OperationSub();
    }
}

public class MulFactory implements IFactory {
    public Operation CreateOperation()
    {
        return new OperationMul();
    }
}

public class DivFactory implements IFactory {
    public Operation CreateOperation()
    {
        return new OperationDiv();
    }
}

客户端实现：

public class Calc {
    public static void main(String args[])
    {
        IFactory operFactory=new DivFactory();
        Operation oper=operFactory.CreateOperation();
        oper.setNumberA(1);
        oper.setNumberB(2);
        double result=oper.GetResult();
        System.out.println(result);
    }
}