question: public void addNodeKeys ( ArrayList < SpatialKey > list , Page p ) { if ( p != null && ! p . isLeaf ( ) ) { for ( int i = 0 ; i < p . getKeyCount ( ) ; i ++ ) { list . add ( ( SpatialKey ) p . getKey ( i ) ) ; addNodeKeys ( list , p . getChildPage ( i ) ) ; } } }
target:  Add all node keys (including internal bounds) to the given list. This is mainly used to visualize the internal splits.