error: compareTo(Object) in Car cannot implement compareTo(T) in Comparable

Question

public int compareTo(Object another) throws CustomMadeException
{
    if(this.getClass() != another.getClass() )
    {
        throw new CustomMadeException();
    }

    Car other = (Car) another;


    return this.getBrand().compareTo(other.getBrand());


}

I don't understand what's wrong exactly with my code. Why can't it implement T in comparable? Do I have to change the argument of compareTo to T? But shouldn't it be Object? As far as I know, the implementation of compareTo in the interface comparable is blank.

Answer 1

The canonical way to do this is as follows:

public class Car implements Comparable<Car> {

    ...

    public int compareTo(Car other)
    {
        return this.getBrand().compareTo(other.getBrand());
    }
}

Note that your implementation of compareTo() can't throw any checked exceptions, since none are permitted by the Comparable<T>.compareTo()'s throws specification.