private TreeNode<?> traverse(Enumeration children) {
if (children.hasMoreElements()) {
TreeNode<?> node = (TreeNode<?>) children.nextElement();
nodes.push(node);
Enumeration newChildren = Collections.enumeration(node.getChildren());
childrenEnums.push(newChildren);
return traverse(newChildren);
} else {
childrenEnums.pop();
TreeNode<?> next = nodes.peek();
nodes.pop();
return next;
}
}
private TreeNode<?> traverse(Enumeration children) {
// If more children are available step down.
if (children.hasMoreElements()) {
TreeNode<?> child = (TreeNode<?>) children.nextElement();
childrenEnums.push(Collections.enumeration(child.getChildren()));
return child;
}
// If no children are left, we return to a higher level.
childrenEnums.pop();
// If there are no more levels left, there is no next
// element to return.
if (childrenEnums.isEmpty()) return null;
else {
return traverse((Enumeration) childrenEnums.peek());
}
}
PostOrderEnumeration(TreeNode<?> node) {
nodes.push(node);
childrenEnums.push(Collections.enumeration(node.getChildren()));
}
PreOrderEnumeration(TreeNode<?> node) {
next = node;
childrenEnums.push(Collections.enumeration(node.getChildren()));
}