private void populatePreOrder(TreeNode<T> currentNode, final LinkedList<TreeNode<T>> stack) {
List<TreeNode<T>> children = currentNode.getChildren();
stack.addLast(currentNode);
for (TreeNode<T> childNode : children) {
populatePreOrder(childNode, stack);
}
}
private void populateInOrder(TreeNode<T> currentNode, final LinkedList<TreeNode<T>> stack) {
List<TreeNode<T>> children = currentNode.getChildren();
if (children.size() == 0) {
stack.addLast(currentNode);
} else if (children.size() == 1) {
stack.addLast(currentNode);
populateInOrder(children.get(0), stack);
} else if (children.size() == 2) {
populateInOrder(children.get(0), stack);
stack.addLast(currentNode);
populateInOrder(children.get(1), stack);
} else {
throw new IllegalArgumentException(
"Can't create an in-order iterator for a node with " + children.size() + " children.");
}
}
