Is memory allocated for unused fields in Java?

Question

I'm wondering how the memory allocation works in Java.

I have a class Duck with two instance variables int size and String name . These variables are initialised. Does the memory for these variables get allocated on the heap during run time, if I'm not instantiating this class?

Thanks, Gene

Answer 1

Several possible scenarios:

• If you are not using a class, then the class itself is not loaded in a class loader at all.

• If you are using a class, but not instantiating it, then instance variables are not occupying memory since there is no instance to begin with.

• If you are using a class, and using an object which is instance of that class, then instance variables are using up memory for each instance, regardless of whether you use these values or not.

Answer 2

如果你没有引用类，所有类的Duck甚至都没有通过类加载器加载，所以答案是否定的。