Question

EDIT: Solved. Returning a 0 works, apparently!

Ok so long story short, I have to return an int value, but nothing when a Linked List is empty. How do I do it?

public int countDuplicates() {

int duplicates = 0;

ListNode current = front;

int num = current.data;
current = current.next;

while(current != null) {
    if(current.data == num) {
        duplicates++;
    } else {
        num = current.data;
    }
    current = current.next;
}
return duplicates;
}

When I try this:

if(front == null) {
    return ;
}

This doesn’t work. What can I do?

Answer 1

To keep the code as you have it now, you must either return an int, throw an exception, or exit.

1. Return an int: You’ll have to specify a certain int value as the "fail" value and make sure that it is never the case that this value is hit during "normal" execution.

2. Throw an exception: Detailed in another answer – you’ve already shot it down.

3. Exit the program… if it makes sense to do that.

The best option may be to change the code – make the function return an Integer, for example, so the null option is there. There are surely other ways to work around it, as well.