i want you to be an experienced java developer and then using an example to teach me what is the difference of the variable which are both hold a subclass object one variable type of parent class anot

Sure, I'd be happy to explain the difference between these two types of variables using an example.

Let's say we have a class hierarchy like this:

class Animal {
    // Animal class code
}

class Dog extends Animal {
    // Dog class code
}

Now, let's create an instance of the Dog subclass and assign it to two different variables:

Dog myDog = new Dog();
Animal myAnimal = myDog;

In this example, myDog is a variable of type Dog, which is a subclass of Animal. myAnimal is a variable of type Animal, which is the parent class of Dog.

The main difference between these two variables is how they can be used. Because myDog is of type Dog, it can be used to call methods and access fields that are specific to the Dog class. For example, if the Dog class had a method called bark(), we could call that method using myDog.bark().

On the other hand, because myAnimal is of type Animal, we can only call methods and access fields that are defined in the Animal class. We cannot call the bark() method using myAnimal.bark(), because that method is not defined in the Animal class.

However, because myAnimal is a variable of type Animal, we can assign any object that is an instance of the Animal class (or any of its subclasses) to it. This means that we could also assign an instance of another subclass of Animal to myAnimal, like this:

Cat myCat = new Cat();
myAnimal = myCat;

In summary, the main difference between a variable of a parent class and a variable of a subclass is that the parent class variable can only access methods and fields that are defined in the parent class, while the subclass variable can access both parent and subclass-specific methods and fields. However, because the parent class variable can hold any object of its type or any of its subclasses, it allows for greater flexibility in assigning and using objects.