靜態抽象方法解決方法

Question

我想在abstract class中創建一個abstract static method。我很清楚從this question這是不可能在Java中。什麼是默認的解決方法/思考問題的替代方式/是否可以選擇這樣做看似有效的示例（如下所示）？

動物類和子類：

我有一個基類Animal與各子類。我想強制所有的子類能夠從一個XML字符串創建一個對象。對於這一點，除靜態以外沒有任何意義嗎？ E.g：

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 
    } 
} 

所以在我需要一個靜態方法，我需要迫使所有子類有這個靜態方法的實現方式的情況下，是有辦法，我能做到這一點？

Answer 1

您可以創建一個工廠，生產動物對象，下面是給你一個啓動一個樣本：

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 
    } 
}