polymorphism in java

[mickey]

hello,

I know that in C++ every time I have a "virtual" method or I derive from a class with virtual method, compiler creates a Vtable for each class:

class Instrument {
   virtual play() { ................}
};
 
class Guitar: public Instrument {
   play() { playNote(); } //1
};
 
Instrument* i = new Guitar();
i-> play(); //call 1

class Instrument {
   virtual play() { ................}
};

class Guitar: public Instrument {
   play() { playNote(); } //1
};

Instrument* i = new Guitar();
i-> play(); //call 1

To copy to clipboard, switch view to plain text mode 

Here compiler builds two Vtable, for Instrument and for Guitar (it doens't clear why a vtable for Instrument)....)

However, what does java do? I mean, I know all methods are "virtual" in java by default; then every class has it's vtable by default? Or the vtable is created only at the moment compiler/interpreter see something like "
Instrument* i = new Guitar();"

thanks,