memory allocation for upcasting in java

不打扰是莪最后的温柔 提交于 2019-12-07 14:24:57

问题


Considering these classes:

public class Animal{

}

public class Dog extends Animal{

}

public AnimalTest(){
    public static void main(String[] args){
       Dog d = new Dog();
       Animal a = d;
   }
}

my question is since I performed an upcasting on Animal a = d;does it consume a new memory allocation on the machine or does it use the memory allocated to the Dog d = new Dog();


回答1:


Animal a = d;

a is just a reference and the reference's memory is allocated in method stack(or jvm stack, not heap).

That is when invoke the method main, JVM will allocate a stack which contains the reference's space.




回答2:


The Actual object or its memory footprint is not affected. just a new reference to the object is created. The only difference is that the reference a can only call methods or access attributes that was available in the Super Class Animal.



来源:https://stackoverflow.com/questions/21374682/memory-allocation-for-upcasting-in-java

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