What is factory pattern java

What is factory pattern java

Factory Pattern is the most commonly used in Java One of the design patterns. This type of design pattern is a creational pattern, which provides an optimal way to create objects.

In the factory pattern, we do not expose the creation logic to the client when creating an object, and point to the newly created object by using a common interface.

To put it simply, the factory method is used instead of the new operation. In layman's terms, when you create a new object, you just call the factory method directly. When programming, you need to define a factory interface, which consists of different To implement it with a subclass, define a specific factory class and define a method to generate instances. We can use this method to obtain instances.

Advantages:

1. If a caller wants to create an object, he only needs to know its name.

2. High scalability. If you want to add a product, you only need to extend a factory class.

3. Shield the specific implementation of the product. The caller only cares about the product interface.

Disadvantages:

Every time you add a product, you need to add a specific class and object implementation factory, which doubles the number of classes in the system. To a certain extent, it increases the complexity of the system and also increases the dependence on specific classes of the system. This is not a good thing.

Application examples:

1. If you need a car, you can pick it up directly from the factory without worrying about how the car is made, and The specific implementation inside this car.

The simple implementation of the factory pattern is as follows:

//所有车的接口  有一个共同改的方法 开车
public interface Car {
    public void drive();
}
//奥迪类  实现car接口因为奥迪车也是车 肯定可以开的嘛
public class Audi implements Car {
    public Audi(){
        System.out.println("生产出一辆奥迪");
    }
    @Override
    public void drive() {
        System.out.println("开奥迪");
    }
}
//宝马类  实现car接口因为宝马车也是车 肯定也可以开
public class Bmw implements Car{
    public Bmw(){
        System.out.println("生产出一辆宝马");
    }
    @Override
    public void drive() {
        System.out.println("开宝马");
    }
}
//生产车的工厂  该工厂接收一个车名 你只需要告诉他你要生产什么车  就可以生产出对应的车出来
public class CarFactory {
    public static Car getCar(String caename){
        if(caename.equals("audi")){
            return new Audi();
        }else if(caename.equals("bmw")){
            return new Bmw();
        }
            return null;
    }
}
//测试
public class Test {
    public static void main(String[] args) {
        //告诉工厂类 你需要生产出一辆奥迪车  那么给昂他传一个参数audi进去
        Car audi = CarFactory.getCar("audi");
        //就可以生产出奥迪的车 调用开车的方法就可以开车啦
        audi.drive();
        //宝马类似
        Car bmw = CarFactory.getCar("bmw");
        bmw.drive();
    }
}
输出：
成产出一辆奥迪
开奥迪
生产出一辆宝马
开宝马

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