/**
* If the delegate collection is empty, but the multimap has values for the key, replace the
* delegate with the new collection for the key.
*
* <p>For a subcollection, refresh its ancestor and validate that the ancestor delegate hasn't
* changed.
*/
void refreshIfEmpty() {
if (ancestor != null) {
ancestor.refreshIfEmpty();
if (ancestor.getDelegate() != ancestorDelegate) {
throw new ConcurrentModificationException();
}
} else if (delegate.isEmpty()) {
Collection<V> newDelegate = map.get(key);
if (newDelegate != null) {
delegate = newDelegate;
}
}
}
/**
* Add the delegate to the map. Other {@code WrappedCollection} methods should call this method
* after adding elements to a previously empty collection.
*
* <p>Subcollection add the ancestor's delegate instead.
*/
void addToMap() {
if (ancestor != null) {
ancestor.addToMap();
} else {
map.put(key, delegate);
}
}
/**
* If collection is empty, remove it from {@code map}. For subcollections, check whether the
* ancestor collection is empty.
*/
void removeIfEmpty() {
if (ancestor != null) {
ancestor.removeIfEmpty();
} else if (delegate.isEmpty()) {
map.remove(key);
}
}
WrappedCollection(
@Nullable K key, Collection<V> delegate, @Nullable WrappedCollection ancestor) {
this.key = key;
this.delegate = delegate;
this.ancestor = ancestor;
this.ancestorDelegate = (ancestor == null) ? null : ancestor.getDelegate();
}
