静态抽象方法解决方法

Question

我想在abstract class 中创建一个abstract static method。我从this question 很清楚，这在 Java 中是不可能的。什么是默认的解决方法/思考问题的替代方式/对于看似有效的示例（如下面的示例）是否可以选择执行此操作？

动物类和子类：

我有一个带有各种子类的基本 Animal 类。我想强制所有子类能够从 xml 字符串创建对象。为此，除了静态之外，它没有任何意义吗？例如：

public void myMainFunction() {
    ArrayList<Animal> animals = new ArrayList<Animal>();
    animals.add(Bird.createFromXML(birdXML));
    animals.add(Dog.createFromXML(dogXML));
}

public abstract class Animal {
    /**
     * Every animal subclass must be able to be created from XML when required
     * (E.g. if there is a tag <bird></bird>, bird would call its 'createFromXML' method
     */
    public abstract static Animal createFromXML(String XML);
}

public class Bird extends Animal {
    @Override
    public static Bird createFromXML(String XML) {
        // Implementation of how a bird is created with XML
    }
}

public class Dog extends Animal {
    @Override
    public static Dog createFromXML(String XML) {
        // Implementation of how a dog is created with XML
    }
}

所以如果我需要一个静态方法，并且我需要一种强制所有子类实现这个静态方法的方法，有没有办法可以做到这一点？

Answer 1

您可以创建一个工厂来生产动物对象，下面是一个示例，让您开始：

public void myMainFunction() {
    ArrayList<Animal> animals = new ArrayList<Animal>();
    animals.add(AnimalFactory.createAnimal(Bird.class,birdXML));
    animals.add(AnimalFactory.createAnimal(Dog.class,dogXML));
}

public abstract class Animal {
    /**
     * Every animal subclass must be able to be created from XML when required
     * (E.g. if there is a tag <bird></bird>, bird would call its 'createFromXML' method
     */
    public abstract Animal createFromXML(String XML);
}

public class Bird extends Animal {
    @Override
    public Bird createFromXML(String XML) {
        // Implementation of how a bird is created with XML
    }
}

public class Dog extends Animal {
    @Override
    public Dog createFromXML(String XML) {
        // Implementation of how a dog is created with XML
    }
}

public class AnimalFactory{
    public static <T extends Animal> Animal createAnimal(Class<T> animalClass, String xml) {
          // Here check class and create instance appropriately and call createFromXml
          // and return the cat or dog
    }
}