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

Every object has a toString() method. That's why you can print every object.

System.out.println(anyObject) -> calls toString() so you don't need to write System.out.println(anyObject.toString());

Your class RealNumb need to override toString().

public class RealNumb{

private Number n;

@Override
public String toString{

return n.toString();

}

}

You can also have a look into this code:
https://code.sololearn.com/cK2H7CdVEq45/?ref=app

Answer 2

https://code.sololearn.com/cF9J5D55GT94/?ref=app

Answer 3

Can you please check my Code? I am getting an error "String cannot be converted to Realnumber".

Answer 4

The problem is here:
public Realnumber addition(Realnumber s)
{
Realnumber p=new Realnumber (r+s.r);

// ERROR:String cannot be converted to String
return toString(p);
}

you need to return p.
toString() returns a String

Answer 5

Preet
Or else try like this
for your requirement,

Change addition and toString function return types to double.
and return double value directly from toString function.