How to construct a LinkedList using a for-each loop in Java?

Question

I'm trying to figure out a way to construct a LinkedList with a for-each loop.

I've put the way I currently have it and it works. I just find it to be very ugly, since I have to declare a single listNode outside the loop and the rest inside a for loop. I just can't shake the feeling this is a clumsy solution.

How It's written-

private listNode nameList;

public listManager(ArrayList<String> names) {
    nameList = new listNode(names.get(0));
    listNode current = nameList;
    for (int i = 1;  i < names.size(); i++) {
        current.next = new listNode(names.get(i));
        current = current.next;
    }
}

I want to use a for-each loop and make everything just a bit more readable but I get the problem of trying to get current.next when current is null so I get a nullpointerexception. Any ideas?

How I would like it would ideally like it written but doesn't work-

listNode current = nameList;
for (String person : names) {
    current.next = new listNode(person);
    current = current.next;
} 

Any help would be appreciated! :)

Answer 1

From my comment:

If you want to use an enhanced for loop i.e. a foreach then you should do the null check inside it.

nameList = null;
listNode current = null;
for (String person : names) {
    if (nameList= null) {
        nameList = new listNode(names.get(0));
        current = nameList;
    } else {
        current.next = new listNode(person);
        current = current.next;
    }
}

Another recommendation: use CamelCase for your class names for better code readability, listNode class should be ListNode and listManager class should be ListManager.

---

By @corsiKa's comment, this won't be a best suited case to use an enhanced for loop (in fact, this really depends on how many items we're talking about to measure the performance impact, but that's outside of this question). To make it a more generic algorithm that can even supports List (the generic interface implemented by ArrayList), you can use an Iterator instead:

Iterator<String> iterNames = names.iterator();
if (iterNames.hasNext()) {
    nameList = new listNode(iterNames.next());
    listNode current = nameList;
    while (iter.hasNext()) {
        current.next = new listNode(iterNames.next());
        current = current.next;
    }
}

Note that if you still want to stick with the enhanced for loop approach, there's no way to remove the null check from it.