Interviewer: what is the factory method mode?

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Preface

Today's electronic sewing machine factory is still in full swing , The boys are full of energy to marry their wives , Step on the sewing machine pedal under your feet and smoke , Just when I concentrated on my work and reached a state of man-machine integration , Suddenly the door of the factory opened from the outside , Here comes a new colleague , In line with the principle of not having to watch your own excitement , Like everyone else, I slowly moved my eyes to the door .

Why ~, Why does this person look so familiar ？ Isn't this wanghong battery brother , How can he come to work .

Take advantage of lunch , I found the battery brother .

I ：“ Battery brother , You claim that you can't work , Why did you come here to work .”

Battery brother ：“ I didn't come to work , I'm here to work .”

I ：“ You made me speechless ... Who said you came to work , I'm curious .”

Battery brother ：“ No one persuaded me , I saw the advertisement at the entrance of the village , I'm going to earn money to find a mother-in-law .”

I ：“ The advertising effect is really good , Easy to understand and attractive .”

Just then my cell phone suddenly rang .

I ：“ feed , Who is this ！”

other party ：“ I , I called you for an interview yesterday , Is it convenient for you now , Let's talk again .”

I ：“ convenient , It's convenient for me to answer the phone as long as it's at work .”

One 、 interview

interviewer ： Let's talk about the factory method mode today , Tell me about your understanding of the factory method pattern ？

I ： The factory method pattern is an extension of the simple factory pattern , It inherits the advantages of the simple factory model , At the same time, it makes up for the defects of the simple factory model .

interviewer ： Can you talk about the advantages of factory method mode over simple factory mode ？

I ： In the factory method pattern, the logic in our factory class corresponds to the parameters passed in , If you want to buy apples , Then you have to have the judgment logic of generating Apple instances according to Apple parameters in the factory class , When you suddenly want to eat pineapple , If there is no logic of this block in the factory class , You have to add this piece of logic to the factory class , In this way, you will frequently modify the code in the factory class , This is not in line with the opening and closing principle .

The factory method pattern adds a specific factory between the factory class and the product , Our specific products are produced through specific factories , There is no need to modify the logic in the factory class .

For example, we were “ How sweet the orchard ”, If you want to eat apples, call our factory directly and we will mail you a box of apples . But now our business has expanded , We started raising poultry , If you want to eat chicken, you can also call us , But this time it's back “ How sweet the orchard ” It's a little inappropriate to call .

So I now set up a Chico Group , If you want something to eat, just call Qige Group , If you want to eat apples , Just call Qige Group , Then Chico group gave it to its subordinates “ How sweet the orchard ” Call and mail you a box of apples , If you want to eat chicken , You also call Chico Group , Then Chico gave it to his subordinates “ It's really delicious. Chicken coops ” Call you and mail a chicken .

interviewer ： Let's talk about the roles of the factory method model ！

1、Product（ Abstract product ）： It defines the interface of the product , Here he is equivalent to a box of fruit , Or a cage for chickens .

2、ConcreteProduct（ Specific products ）： He implements the abstract product interface , He is equivalent to Apple or chicken here .

3、Factory（ Abstract factory ）： He is equivalent to the Chico group here , It is used to receive calls from customers , Then give the customer a box of fruit or a cage of chicken .

4、ConcreteFactory（ Specific factory ）： Here he is equivalent to “ How sweet the orchard ” perhaps “ It's really delicious. Chicken coops ”, He is responsible for receiving calls from the group and then giving corresponding products to the Group .

interviewer ： Can you write specific code to describe the factory method pattern ？

1、 First, define a box interface , This represents the abstract product role

public interface Box {
    
    public void show();
}

2、 Then define an apple class , This represents specific products

public class Apple implements Box {
    
    @Override
    public void show() {
    
        System.out.println(" Bought a box of apples ");
    }
}

3、 Then define a Chico group class , This represents an abstract factory

public interface FactoryQG {
    
    public void show(String name); // Abstract factory methods 
}

4、 Then define a “ It's delicious ” class , This represents a specific factory

public class Zxy implements FactoryQG {
    
    Box box = null;
    @Override
    public void show(String name) {
    
        if(name.equals(" Apple ")){
    
            box = new Apple();
            box.show();
            System.out.println(" It's really delicious. Orchard apples ,50 Yuan per box ");
        }
    }
}

5、 Final test

public class Test {
    
    public static void main(String[] args) {
    
        FactoryQG factoryQG = new Zxy();
        factoryQG.show(" Apple ");
    }
}

Through the above process, we can see , If you need to add one at this time “ Chicken coop ”, Just add a specific factory class , There is no need to modify the code of the abstract factory class , This is in line with the opening to expansion , Turn off for changes .

interviewer ： Boy... Yes , When will you have time to join the company ？

I ： To say again , I'll finish sewing the autumn pants in my hand first ...

Two 、 summary

The relevant contents here have not been sorted out yet , The article continues to be updated later , Recommended collection .

The commands involved in the article must be typed several times each like me , Only in the process of knocking can you find out whether you really master the command .

If you think my article is good, just like it , In addition, you can search through wechat 【 Xiaoqi JAVA interview 】 First time reading , reply 【 Information 】 What's more, I have prepared welfare for you ！ reply 【 project 】 I have some project source code for you . reply 【 The resume template 】 There is a resume template I prepared for you .