/**
* Creates the levels higher than the given level
*
* @param boundablesOfALevel the level to build on
* @param level the level of the Boundables, or -1 if the boundables are item boundables (that is,
* below level 0)
* @return the root, which may be a ParentNode or a LeafNode
*/
private AbstractNode createHigherLevels(List boundablesOfALevel, int level) {
Assert.isTrue(!boundablesOfALevel.isEmpty());
List parentBoundables = createParentBoundables(boundablesOfALevel, level + 1);
if (parentBoundables.size() == 1) {
return (AbstractNode) parentBoundables.get(0);
}
return createHigherLevels(parentBoundables, level + 1);
}
/**
* Sorts the childBoundables then divides them into groups of size M, where M is the node
* capacity.
*/
protected List createParentBoundables(List childBoundables, int newLevel) {
Assert.isTrue(!childBoundables.isEmpty());
ArrayList parentBoundables = new ArrayList();
parentBoundables.add(createNode(newLevel));
ArrayList sortedChildBoundables = new ArrayList(childBoundables);
Collections.sort(sortedChildBoundables, getComparator());
for (Iterator i = sortedChildBoundables.iterator(); i.hasNext(); ) {
Boundable childBoundable = (Boundable) i.next();
if (lastNode(parentBoundables).getChildBoundables().size() == getNodeCapacity()) {
parentBoundables.add(createNode(newLevel));
}
lastNode(parentBoundables).addChildBoundable(childBoundable);
}
return parentBoundables;
}