upcasting and downcasting

Question

I am having the following method:

//Number is an abstract class
//I am passing an object as a 1.argument and the 2nd argument is the instanzvariable itself
public Number addition(Number n)
{
Realnumb r=(Realnumb)n;//downcasting

Number n=new Realnumb(a+r.a);

}

public String toString()
{
}

Main method:

Number n1=new Realnumb(3.0);
Number n2=new Realnumb(5.0);

System.out.println(n1.addition(n2));

The result should be 8.0.

My question is how to call the "toString" method in the method "addition"? As I am having a method of type "Number", what should be the return value?

Answer 1

Its better to specify full code or related full code.

Actually print the corresponding object. then It implicitly calls toString() function.
or you can call explicitly through object.