关于java：工厂方法与抽象工厂

Factory Method Vs Abstract Factory

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我读过工厂方法，其中子类创建所需对象，抽象工厂有方法，其中具体类创建所需对象。

工厂法

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public class PizzaStore {

public Pizza orderPizza(String type) {
Pizza pizza = createPizza(type);
pizza.prepare();
pizza.bake();
pizza.cut();
}

abstract Pizza createPizza(String type);

}

public NewYorkPizzaStore extends PizzaStore {

public Pizza createPizza(String type) {
Pizza pizza = null;
if("cheese".equals(type)) {
pizza = new CheesePizza();
}
else if("onion".equals(type)) {
pizza = new OnionPizza();
}

return pizza;
}

}

public class pizzaTestDriveByFactoryMethod() {

public static void main(String args[]) {
PizzaStore ps = new NewYorkPizzaStore();
ps.orderPizza("cheese");
}

}

使用工厂

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public class NewYorkPizzaFactory extends PizzaFactory {

public Pizza createPizza(String pizza) {
Pizza pizza = null;
if("cheese".equals(type)) {
pizza = new CheesePizza();
} else if("onion".equals(type)) {
pizza = new OnionPizza();
}

return pizza;
}

}

public class PizzaStore {

PizzaFactory factory;

public PizzaStore(PizzaFactory factory) {
this.factory = factory
}

public Pizza orderPizza(String type) {
Pizza pizza = factory.createPizza(type)
pizza.prepare();
pizza.bake();
pizza.cut();
return pizza;
}

}

public class pizzaTestDriveByAbstractFactory() {

public static void main(String args[]) {
PizzaFactory nwFactory = new NewYorkPizzaFactory();
PizzaStore ps = new PizzaStore(nwFactory);
ps.orderPizza("cheese");
}

}

使用工厂方法和抽象工厂实现相同的用例。为什么应该使用FactoryMethod而不是抽象工厂或实用工厂(如芝加哥工厂/纽约工厂)。在哪种情况下，工厂方法对抽象方法有用？