+ /*
+ * DEFAULTS
+ */
+ // - no children
+ // - no attributes
+ // - cannot be modified
+ @Override
+ public Iterator<Content> iterator() {
+ return Collections.emptyIterator();
+ }
+
+ @Override
+ public Content add(QName name, QName... classes) {
+ throw new UnsupportedOperationException("Content cannot be added.");
+ }
+
+ @Override
+ public void remove() {
+ throw new UnsupportedOperationException("Content cannot be removed.");
+ }
+
+ protected Iterable<QName> keys() {
+ return Collections.emptySet();
+ }
+
+ @Override
+ public <A> Optional<A> get(QName key, Class<A> clss) {
+ return null;
+ }
+
+ protected void removeAttr(QName key) {
+ throw new UnsupportedOperationException("Attributes cannot be removed.");
+ }
+