Using Iterator with LinkedList

[Dave DiRito]

I'm trying to use an iterator in a method to count the number of duplicates in a list of integers. I have a logic problem in it somewhere because it only counts one set of duplicates every time even if there's more than one. Here's the code:

    public static Integer countDups(LinkedList<Integer> list){
Iterator<Integer> itr = list.iterator();
int previous, next, dups = 0;
previous = itr.next();
while(itr.hasNext()){
    next = itr.next();
    if(previous == next){
previous = next;
dups++;
    }
}
return dups;    
    }

Thanks,
Dave

[Dave DiRito]

Just figured it out:

public static Integer countDups(LinkedList<Integer> list){
Iterator<Integer> itr = list.iterator();
int previous, next = 0, dups = 0;
previous = itr.next();
while(itr.hasNext()){
    next = itr.next();
    if(previous == next){
dups++;
    }
    previous = next;
}
return dups;    
    }

[Dave DiRito]

Also, the list must be sorted for this method to work. I used Collections.sort(list); before passing the list to the method.

[Rob Spoor]

You'd better not use == comparison even for Integers. Use equals() instead, and beware of null values.