static <L> Tree<L> stripLeaves(Tree<L> tree) {
if (tree.isLeaf()) return null;
if (tree.isPreTerminal()) return new Tree<L>(tree.getLabel());
List<Tree<L>> children = new ArrayList<Tree<L>>();
for (Tree<L> child : tree.getChildren()) {
children.add(stripLeaves(child));
}
return new Tree<L>(tree.getLabel(), children);
}
private int addConstituents(Tree<L> tree, Set<Object> set, int start) {
if (tree.isLeaf()) {
if (punctuationTags.contains(tree.getLabel())) return 0;
else return 1;
}
int end = start;
for (Tree<L> child : tree.getChildren()) {
int childSpan = addConstituents(child, set, end);
end += childSpan;
}
L label = tree.getLabel();
if (!labelsToIgnore.contains(label)) {
set.add(new LabeledConstituent<L>(label, start, end));
}
return end - start;
}