public Iterator<TreeNode> findChildren(){
  List<TreeNode> nodes;
  if (children == null)   nodes=Collections.emptyList();
 else   nodes=children;
  return nodes.iterator();
}

public Iterator < TreeNode > findChildren ( ) { List < TreeNode > nodes ; if ( children == null ) nodes = Collections . emptyList ( ) ; else nodes = children ; return nodes . iterator ( ) ; }
return an iterator of all children of this node . if there are no children , an empty iterator is returned .
