Type mismatch question

Question

Hi,
I am tasked to create a class called Dollars with a constructor that takes in a double value.
In addition, this class has a method add, which is supposed to be of return type Dollars add(Dollars dollars).
I know I need to return a _value in a Dollars type. However, it is currently in a double type.
Trying to cast it into return (Dollars)_value won't work. Can anyone give me some advice on how to attain a method of of return type Dollars add(Dollars dollars)?
class Dollars{
     protected double _value;
     public Dollars(double value)
     {_value=value;
     public double getValue(){
          return this._value;
     public Dollars add(Dollars dollars)
          _value +=dollars.getValue();
          return _value;
}

Answer 1

double is a primitive, not an extendable class, and casting overloads do not exist in Java. What you can do is create and return a new Dollars object:
return new Dollars(this.value + dollars.getValue());Or return the existing one:
this.value += dollars.getValue();
return this;