Classes Dog dog = new Dog(); what dose this acctualy do?

Question

For the example Dog is an class.
I have been wondering about the following lines of code:

Dog dog = new Dog();

in comparance to this code:

Dog dog;
dog = new Dog();

I'm not sure if I have understood all what I have read inn the books and articles I'm learning from but the
Dog dog;
is the same as declearing a variable like an int "int myInt;" it only creates a space inn memory to store such int,
or inn the case of the dog it creates a place to store a Dog instance and lables it "dog" so you can refer to that place as dog?

so when you do
dog = new Dog();
you actually give the dog the information of Dog?
can you only set it as new Dog or could I set it as a new of another class than dog?

Vulpes · Answer

'dog' is a variable of type Dog and as Dog is a class it will contain a reference (i.e. a pointer) to where an instance of the Dog class is stored elsewhere in memory These sets of statements do exactly the same thing: Dog dog = new Dog(); // allocates memory and assigns a reference to a new Dog instance // or Dog dog; // allocates memory for the variable dog = new Dog(); // assigns a reference to a new Dog instance to the variable You can only assign references to Dog instances to the 'dog' variable though if you have a class which inherits from Dog (say Puppy) then you could assign an instance of the sub-class to 'dog' as well. For example: Dog dog = new Puppy();

Classes "Dog dog = new Dog();" what dose this acctualy do?