创建型 - 工厂方法(Factory Method)

工厂方法

它定义了一个创建对象的抽象方法，但由子类去实现该方法决定要实例化哪个类。工厂方法把实例化操作推迟到子类，模式上使用了继承

代码实现

public abstract class Factory {
    abstract public Product factoryMethod();
    public void doSomething() {
        Product product = factoryMethod();
        // do something with the product
    }
}

public class ConcreteFactory extends Factory {
    public Product factoryMethod() {
        return new ProductA();
    }
}

public class ConcreteFactory1 extends Factory {
    public Product factoryMethod() {
        return new ProductB();
    }
}