Java instanceof 解析记录

instanceof在实际开发中常用于类型强转时的判断，如在项目中不进行判断进行强制转换会出现类型转换异常

public interface Animal{

}

public class Animalmpl implements Animal{

}

public class Dog extend Animalmpl {

}

public class DogSon extend Animalmpl {

}

void test(){

 Animalmpl dog_animalmpl = new Dog()

 Dog dogson_dog = new DogSon()

 Animalmpl dogson_animalpl = new DogSon()

 Animal dogson_animal = new DogSon()

 

System.out.println(dog_animalmpl instanceof Animalmpl );//返回true

System.out.println(dog_animalmpl instanceof Animal );//返回true

System.out.println(dogson_dog instanceof DogSon);//返回true

System.out.println(dogson_dog instanceof Dog );//返回true

System.out.println(dogson_dog instanceof Animalmpl );//返回true

System.out.println(dogson_dog instanceof Animal );//返回true

System.out.println(dog_animalmpl instanceof dogson_dog );//返回false

总结：

如果   A instanceof B

用于判断A的具体实现对象，B为A的父类、A父类的实现接口、A本身时返回true

B为A的子类或者A本身为null时返回false

 

}