设计模式之工厂方法模式

工厂方法模式

定义一个创建对象的接口，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了子类。

Operation类

package com.hml.factory.method;

public abstract class Operation {

    private int numberA;
    private int numberB;

    public int getNumberA() {
        return numberA;
    }

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

    public int getNumberB() {
        return numberB;
    }

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

    public abstract int getResult();
}

AddOperation类

package com.hml.factory.method;

public class AddOperation extends Operation {

    public int getResult() {
        return getNumberA() + getNumberB();
    }

}

SubOperation类

package com.hml.factory.method;

public class SubOperation extends Operation {

    public int getResult() {
        return getNumberA() - getNumberB();
    }

}

IFactory类

package com.hml.factory.method;

public interface IFactory {
    public Operation createOperation();
}

AddOperationFacotry类

package com.hml.factory.method;

public class AddOperationFactory implements IFactory {

    public Operation createOperation() {
        return new AddOperation();
    }

}

package com.hml.factory.method;

public class SubOperationFactory implements IFactory {
    public Operation createOperation() {
        return new SubOperation();
    }
}

类图

 工厂方法模式实现时，客户端需要决定实例化哪一个工厂来实现运算类，选择判断的问题还是存在的，也就是说，工厂方法把简单工厂的内部逻辑判断移到了客户端代码来进行，想要增加功能，本来是修改工厂类，而现在是修改客户端代码。