Use Of Interface(Memory Consume)

Question

I have a doubt
//Interface A
code:
interface A{
public void add();
public void sub();
public void multiplication();
//Class B that Implements A
class B implements A{
public void add(){
int a=30;
int b=40;
int c=a+b;
System.out.println("The result of Addition is:-"c);
public void sub(){
int a=80;
int b=40;
int c=a-b;
System.out.println("The result of Substraction is:-"c);
public void multiplication(){
int a=80;
int b=40;
int c=a*b;
System.out.println("The result of Multiplication is:-"c);
public void division(){
int a=80;
int b=40;
int c=a/b;
System.out.println("The result of Division is:-"c);
//Anaother class C that use B's method
class C{
public static void main(String[]args){
//what is the differnce
//I have a doubt why we use this line
A a=new B();
a.add();
B b=new B();
b.add();
I have a doubt,In class C I am accessing the B's add()through 2 referance variables one is class type and another is interface type.ok
My doubt is what's the differance?
which is adviceable to use?
if Interface reference is advisable,weather it will allocate memory at runtime or compile time?
a class variable will allocate memory at runtime or compile time?
thanks
Biswo
Edited by: Biswo on Dec 3, 2008 8:29 AM

Answer 1

Biswo wrote:
My doubt is what's the differance?
which is adviceable to use?They're equivalent from a performance standpoint so it boils down to whether you want the reference variable to be of type A or B, which is a design consideration.
In both cases the B object is allocated at runtime and the add method is bound at runtime.
The Java language is very efficiently implemented so you don't have to worry about things like this. Concentrate on proper design instead.